App Manual

You can use Rubberduck for free. The basics are free: voyages & legs, GPS track & map, logbook entries, trip photos, anchor watch, area news & area alerts, harbour search, ⚓ anchorage forecast, sun times/currency, single-trip PDF, Kielwasser publishing and share cards.

Rubberduck Premium (subscription or one-time purchase) additionally unlocks: NMEA live instruments, weather & tides, night watch, safety briefing, ship management (maintenance, repairs, spare parts, documents, inventory), packing list, ship's kitty, watch schedule, annual/collected PDF, offline nautical charts and iCloud/multi-device sync.

Premium features are marked with a lock; tap it to open the unlock screen. Existing subscriptions and purchases remain unchanged.

Rubberduck distinguishes between Voyages (multi-leg passages) and Legs (individual day sails or route segments). A Voyage groups multiple Legs — ideal for multi-day crossings with several ports.

Create a voyage: Tap 'New Voyage' at the top of the passages list. Enter name, ship and skipper. Optionally select crew as voyage participants — only these appear in the Cash Box and Watch Schedule. The voyage shows tabs for Legs, Cash Box and Watch Schedule.

Start a leg: Open a voyage and tap +. You can also start any passage without a voyage — just tap + in the main list.

Delete a leg or detach it from the voyage: In the voyage view, every leg card has a visible red trash button at the top right — it deletes the leg permanently (with a confirmation prompt; log entries and track are lost). Using the ⋯ menu next to it you can instead 'Detach from voyage', turning the leg into a standalone single leg. Single legs (without a voyage) are deleted in the passages list by swiping left.

Tap the + button in the passages list (or inside a voyage). Select your ship and skipper. For a sailboat, choose propulsion: Under Sail (with optional sail selection and reef status), Under Engine, or Engine & Sail. Optionally enter engine hours, water tank and fuel tank levels before departure.

Tap 'Start Passage' to begin GPS recording immediately. Weather and forecast are fetched in the background. Tracking runs fully in the background — the device does not need to be unlocked.

Under Settings → 'Tracking & Log' you control recording:

• Route Recording: how often GPS points are saved for the track line (shorter = more accurate curve).
• Sample Rate: how often the position is sampled and the log triggers are checked.
• Log Entries — three independently adjustable triggers (0 = off): time interval (every X minutes), distance (after X nautical miles) and course change (more than X°). Each entry notes the reason, e.g. '↪ After 5 nm' or '↪ Course change >20°'.
• Weather Interval: how often weather is written to the log between start and end (always at start and end).

All values are saved instantly and run independently in the background.

Outlier protection: Implausible GPS jumps (e.g. coarse cell-tower fixes) are discarded automatically — distance and track stay clean. Each point's accuracy is stored as well.

In the detail view of an active passage, add manual log entries at any time — directly from the Propulsion section using the Log button. GPS position is saved automatically.

Automatic entries: GPS route points (per route interval), NMEA weather (every 15 min if connected), online weather (per weather interval), anchor drop/weigh, propulsion change. Visible log entries are created by the triggers set under 'Tracking & Log' (time, distance sailed, course change) — each with avg. speed, distance and the noted reason.

Route Details: In the Details tab, tap 'Route Details' to see all GPS points and log entries in a filterable overview.

You write your own entries in a dedicated input sheet (multi-line); time, position, SOG and COG are added automatically. In the log your text appears highlighted, with the measurements on a grey line below.

Edit & delete: Tap one of your own entries in the log to edit it — the input sheet opens with your text, and you can delete it from there. Alternatively long-press the entry → 'Edit' or 'Delete'. Only your own entries are editable; automatic entries (GPS, weather, anchor, propulsion) stay unchanged. Changes sync via iCloud to all devices.

Quick Entry: While a passage is active, a 'Quick Entry' banner appears above the tab bar. Tapping it opens a sheet with your quick-entry templates (typical events like 'Reef in', 'Engine on', 'Watch change') — one tap immediately writes a log entry with time and position, confirmed by a brief '✓ Logged'. You can also type free text below. Create your own templates per ship under Settings → Ships; they sync via iCloud to all devices.

On passage start, current weather and a 24h forecast are automatically fetched and logged. Online weather updates at the configured interval (default 60 min, adjustable under 'Tracking & Log'). When NMEA is connected, instrument readings (wind, depth, water temp.) are logged every 15 minutes.

The active passage detail shows an hourly forecast strip — cards with Bft ≥ 6 are highlighted in red. Tap 'Refresh Weather Now' to manually fetch current weather at any time.

The Ship tab (second tab) manages your ship across five sections:

• Parameters: Vessel type, NMEA gateway, sails and custom ship parameters (e.g. Diesel tank 120 l, Length 12.5 m). Parameters sync via iCloud.
• Maintenance: Tasks with interval (e.g. oil change every 200 h, antifouling annually), last completion date and next due date. Create custom categories. Overdue tasks are highlighted in red.
• Repairs: Log of completed repairs with date, cost and status. Open repairs remain visible until marked as done.
• Spare Parts: Stock of spare parts with quantity and stowage location (e.g. 'forepeak locker').
• Documents: Ship papers (purchase contract, insurance, registration) as photo or multi-page scan.

All data syncs via iCloud.

Renaming: If you change the ship name, all previous passages, voyages and your Kielwasser log adopt the new name automatically. Sailboats automatically get the 'SY' prefix, motorboats 'MY'. Pick a ship photo right in the ship editor — the 16:9 frame lets you choose the tile crop yourself; it appears on your Kielwasser ship profile and the portal cards.

The Cash Box tracks shared expenses for a voyage. Open a voyage and tap the 'Cash Box' tab.

Expenses: Tap + — description, amount, category and who paid. 'From cash box' is only available while the box is funded (payments minus expenses already paid from it). If the box is empty, the expense must be assigned to a person — so the box never goes negative.

Payments: Record contributions individual crew members pay into the box.

Settlement tab: At the top, use the chips to choose who shares the costs — e.g. exclude a child (the selection is stored permanently on the voyage). Below: total, share per person, balances and the minimal transfers. Use 'Share settlement' to export/print the report, or 'Email settlement' to send it to the crew's stored addresses.

All Cash Box data syncs via iCloud.

Closing: Once the voyage has ended, you can close the cash box in the settlement tab — expenses and payments are then locked while the settlement stays visible. 'Reopen' allows corrections.

Settlement cycles: With a changing crew you can settle the box mid-voyage without ending it — in the settlement tab tap 'Settle up & new cycle'. The current cycle closes and a new one begins; you then adjust its crew (pick existing or add new). The 'who shares' chips apply to the current cycle. Past cycles appear below in the history — tap one to see its settlement with the same share/email actions. All cycles sync via iCloud.

The Watch Schedule assigns watches to the crew. Since 4.4.7 it belongs to a specific leg (passage), no longer to the voyage: open the leg (leg detail) and its Watch Schedule there. New schedules can only be created for an ACTIVE, running leg.

Create a schedule: Tap + and set start date/time, duration (days) and shift length (3 or 4 hours, or 'Alternating' for 3/4 h in turn). Choose the number of people per watch. The crew comes from the leg — you can add existing crew or create new ones directly and drag the order. On creation a log entry is written automatically listing every watch with names and times.

A leg has exactly one watch schedule: if you create a new one, it replaces the existing schedule. The schedule shows the watches in chronological order; individual watches can be reassigned with a tap or deleted one by one by swiping left. You delete the whole schedule via the trash icon in the schedule header (with a confirmation prompt). Every change — reassigning, deleting a single watch or the entire schedule — is recorded as a log entry. Schedules sync via iCloud so the whole crew sees the same state.

Watch change from Quick Entry: while a watch schedule exists for the active leg, Quick Entry shows the current and the next watch. ‘Log watch change’ offers two ways: under ‘From schedule’ a single tap activates the next planned watch together with its team (pre-selected); under ‘Choose crew’ you tick off whoever takes over individually (if reality differs from the plan). The change is written to the logbook with time and position.

Under Settings → Crew you manage your crew members. For each person you can store name, email, phone, date of birth and document number. In the Documents section, save licences, VHF certificates, sailing licences and other certificates as a photo — with issue date and title.

All crew data syncs automatically via iCloud and is included in backups.

When starting a passage you can optionally enter engine hours, water tank and fuel tank levels. In a passage's detail view, find 'Enter End Values' to record the final readings — you can also add them after the passage has ended ('Add End Values'). Engine hours used is calculated automatically. Start and end values are shown in the passage list when available.

Ship's log: Optionally enter the log reading (nm) at start and end — the start value is pre-filled with the last passage's end value. The log distance (through the water) appears next to the GPS distance (over ground) — the difference shows the current. You can also store the log reading and operating hours permanently on the ship (Edit Ship); the next passage picks them up automatically as start values.

The Area tab bundles everything for passage planning at your position: tides, weather and official area news — switch via the segments at the top.

Tides: Stations within 80 nm are shown automatically, or search by name. Tap a station for the 7-day tide curve — current time is marked in red. Tap a day to log all HW/LW values. Data is cached for 2 days and shared via iCloud. During an active passage tides are logged automatically (start, every 48 h, approaching <10 nm of a station).

Weather: Current conditions (wind, temperature, pressure, waves) and the 48-hour forecast at your position — same data source as during a passage, warning cards from Bft 6 in red.

Area news: Official notices to skippers for your area — closures, lock and bridge works, wrecks, events. The app detects your area automatically from your position. Sources: Rijkswaterstaat (NL), ELWIS/WSV (German coast, Kiel Canal, inland), Søfartsstyrelsen (DK) and Sjöfartsverket (SE), updated hourly via kielwasser.blog. Closures are marked in red; the detail view opens the full notice on Kielwasser. Offline you see the last fetched state with its timestamp.

When starting a passage the app additionally checks your area: if there are active closures, a hint appears at the top of the start dialog — tap it to see the notices.

⚠️ The notices are a planning aid and do not replace official notices to mariners for navigation.

Tap the Anchor Watch tab. Enter the safety radius in metres and tap 'Drop Anchor'. The current position is set as the anchor point. The map shows ship movement: green (safe), orange (approaching limit), red (outside). An alarm sounds immediately on breach. This works alongside an active passage. Anchoring and weighing are automatically logged.

Position source & accuracy: With NMEA connected, the anchor watch always uses the vessel position (true GPS). Without NMEA the app shows the device fix accuracy and warns on a coarse fix (e.g. Wi-Fi-only iPad without GPS chip: ±65 m or more) — connect NMEA then, otherwise the alarm is not reliable.

Enter your NMEA gateway's IP and port (default: 10110) in the ship settings. The gateway must be on the same Wi-Fi. The app connects automatically when the ship is selected. Available data: GPS, wind, depth, water temp., pressure, heading. NMEA position always takes priority over device GPS.

If the connection drops, the app retries every 10 seconds. Without NMEA data, the app falls back to online weather. Status indicator: green (connected, current), yellow (connected, no recent data), orange (disconnected).

NMEA monitor: the monitor (in the ship editor) connects to the configured gateway by itself when opened — even without an active passage; without one it disconnects again when closed. If nothing arrives, a hint lists the usual causes: wrong Wi-Fi, missing 'Local Network' permission (iOS Settings → Privacy), or a gateway that allows only one connection at a time.

Self-healing: If the gateway silently switches networks (e.g. adapter moving from Starlink to ship Wi-Fi), the app detects the stalled connection after at most 60 seconds of data silence and reconnects automatically — likewise immediately when the device changes Wi-Fi.

Community depths: When a NMEA depth transducer is connected, the app contributes the water depths measured during the passage anonymously to the community depth map on Kielwasser — there they appear as a depth layer on the harbour detail pages. ⚠️ Rough orientation only, NOT a basis for navigation.

With an NMEA log (STW, speed through water) and a compass heading connected, the app continuously derives the current from the difference between speed over ground (SOG/COG from GPS) and speed through water (STW/heading). It shows drift (current speed in knots), set (the direction the current flows toward) and the along-course component ('with you' / 'against you').

Live, the current appears as a tile in the NMEA monitor and as a line in the active passage. Optionally the app logs the values at a regular interval — set it under More → Tracking & Log (5–120 min). When a passage ends, a current summary (avg/max drift) is appended.

GPS outliers: 'Clean track' (in a passage's ⋯ menu) removes bad fixes (impossible jumps/teleports) from a recorded track and corrects the distance.

Every passage detail shows an embedded map with the route. Start: green, end: red, current position: orange (active passage). The map is interactive. Under Settings → Map choose the provider: Apple Maps, OpenStreetMap or Google Maps.

Seamarks: On all maps (including the PDF/archive export) seamarks from OpenSeaMap are shown automatically — buoys, lights, harbours and sea marks, on top of your chosen base map. Data source: © OpenSeaMap contributors. ⚠️ Note: this is free community data and NOT an official nautical chart — do not use for navigation.

Tip: Under Settings → Map → 'Download maps offline' you can pre-download your area — so map and seamarks are available without internet (at sea).

In the Log tab, buttons let you add photos (camera or library) and manual log entries. Camera photos receive the current GPS position automatically. Library photos without EXIF get the nearest GPS track point.

Edit location: long-press a photo → 'Edit Location'. Enter a place name — the app geocodes it to exact coordinates. Photos are included in backups and PDF exports, and sync to all devices via iCloud.

Open a passage and tap 'Export PDF'. Choose mode: 'Summary' exports overview entries only, 'Detail Report' includes all GPS tracking entries. The PDF includes passage details, map overview (with 📷 pins) and photos in a two-column grid. A share sheet opens.

Annual Export: Tap the magnifier icon in the passages list, select a year, and create a combined PDF of all passages for that year — optionally with a map per passage.

Two steps: The first tap on 'Create PDF' renders the document — with many photos or entries this takes a moment. It runs in the background so the app won't crash even on older devices. Afterwards the share button appears; the second tap opens the share sheet (or the email).

Note: This classic web export only appears if it was set up in the past — the recommended way today is the Kielwasser blog (see its own chapter).

Under Settings → Web Export, publish completed passages to your WordPress site. Enter server URL and API key from WordPress admin. The passage list shows status: 'Not uploaded', 'Online', or 'Outdated'. Tap 'Upload', 'Update', or 'Delete from web'. Each passage gets its own page with map, statistics and photo gallery.

Kielwasser is Rubberduck's blog platform: publish your passages with chart and statistics in your own ship's log on kielwasser.blog — ad-free, your data is yours.

Create a log: Settings → Kielwasser-Blog → enter email and preferred name → tap the confirmation email — the app connects automatically. No password needed.

Publish a passage: In the Kielwasser view tap 'Publish' on a completed passage — track, distance, duration and log excerpt appear with a chart in your log. Your ship is created automatically. Swipe to remove a passage (web trash).

Write a post: Free blog posts with photos — e.g. the harbour day. GPS data is stripped from photos automatically.

Web password: Only for writing and managing in the browser — the app itself is already securely connected.

Delete account: In the Connection section, 'Delete account & blog' permanently removes your log from the server (double confirmation) — your data in the app is kept.

Voyages: Publish a whole trip with all its legs — under 'Voyages'; the legs appear as chapters in the voyage journal.

Logbook detail: With every publish you choose whether the log goes along shortened or complete.

Photos: Up to 20 photos per passage come along (the first becomes the cover), GPS data is stripped. Uploads keep running in the background even if you leave the app — a progress bar shows how far along each upload is.

Ship & profile: Type, home port, registration, MMSI, ATIS, owner, the ship story (its own field in the ship editor, shown as its own card on the profile — left empty it never overwrites text written in the browser) and your custom fields transfer automatically to the ship profile; your 'About me' appears on the skipper page. Measurements like length or draft are added in the browser — the app never overwrites them.

Invite crew: Connection → 'Invite crew' — your crew member gets an invitation email and then writes in the same log in the browser. The app stays with the log owner: one ship, one app.

Reconnect: After disconnecting or switching devices, just use 'Connect existing → Connect by email' — tap the confirmation email, done.

Live position (opt-in): Enable 'Share live position' — during an active passage your log shows your position every few minutes (🔴 live with a mini map; portal cards get a live dot). Without coverage the marker ages honestly ('last position … ago'); it disappears automatically when the passage ends.

Connect via QR (web account): If you created your logbook in the browser, open '📱 Connect app' in your logbook admin and generate the QR code. Scan it with the iPhone camera, confirm in the app — done, no typing. Generating a new QR invalidates the old one.

Area alert (newsletter): Under Settings → Kielwasser-Blog → 'Area alert' you subscribe to the official notices for your areas by email. Pick the areas you want directly in the app, change the selection at any time, or deselect all to unsubscribe. Mail goes to your verified account address — there is no separate email field.

Turn any completed passage into a share card in the Kielwasser design: map image with route, distance, duration and average speed — as a story (9:16) or square (1:1).

Share a leg: Tap the share icon in the passage view.

Share a voyage: In the voyage, use the ⋯ menu → 'Share passage' — the card shows the combined route of all legs with total statistics.

Instagram: If Instagram is installed, 'Share story' opens the story editor directly with your card as the background.

Copy link: For passages published on Kielwasser you can copy the link to your ship's log — WhatsApp, Facebook and forums automatically render a preview with map and statistics, and the recipient lands right on your passage story.

'More options' opens the system share sheet (save, AirDrop, other apps).

Under Settings → iCloud Sync, all data syncs automatically — when a passage ends and when the app goes to the background. Synced data: all passages and legs, voyages, photos, ships, crew, documents, Cash Box expenses and payments, watch schedules, maintenance tasks, repairs, spare parts, tidal data cache and settings.

On a fresh install on a second device, all data is imported on first sync. Tap 'Sync Now' for manual sync. 'Full Resync' re-downloads all content without data loss — useful after a device change.

Note: Active passages are not transferred to other devices until completed.

Under Info & Tools → Daylight Times you see all nine solar events for any location and date:

Astronomical twilight (start/end), nautical twilight, civil twilight, sunrise, solar noon, sunset — each as a local time.

Displayed as a coloured 24h band: night (dark blue), astronomical twilight, nautical twilight, civil twilight, day (yellow). Current time is marked with an indicator.

Location: tap the GPS button (top right) to use your current position, or type a place name into the search field (e.g. 'Palma', 'Kiel', 'Lisbon').

Date: tap the date or use the arrows to navigate. Polar regions show 'Polar Day' or 'Polar Night'.

Under Info & Tools → Currency Converter you convert between 33 currencies — even without an internet connection.

Rates: the app fetches current ECB rates once daily via the free frankfurter.app API. Rates are cached for 24 hours — when offshore with poor connectivity, the last known rates are used automatically.

Usage: enter an amount, choose From and To currencies — the result appears instantly. The date of last update is shown.

Under Info & Tools → Packing List you find a global checklist for your ship — independent of individual passages.

Pre-filled with 7 categories: Navigation, Safety, Provisions, Clothing, Documents, Equipment and First Aid — in your app language.

Usage: tap an item to check/uncheck it. Swipe left to delete. Add new categories with the + button at the bottom; add items within a category with its own +. 'Reset' removes all ticks without deleting any content.

A progress bar shows how many items are checked.

All changes sync automatically via iCloud to all your devices.

Under Info & Tools → Safety Briefing you conduct the mandatory pre-departure safety briefing for your crew.

Checklist: 6 categories — Emergency Equipment, Man Overboard, Fire, Communications, Vessel Safety, First Aid. Prepared in all 10 app languages. Tap items to mark them as covered.

Complete a briefing: select crew members from the list at the top, or add additional participants as free text. Add optional notes. Tap 'Complete Safety Briefing' to save the record with date, participants and checklist status.

Protocol: the Protocol tab shows all previous briefings with date, participants and checked item count. Tap a record for the full detail view. Use the share icon to export the record as text (e.g. by email or AirDrop).

All briefing records sync via iCloud to all your devices.

Under Settings → Info you find five nautical reference tables:

• Beaufort Scale — all 13 wind force levels (0–12) with knot ranges.
• Flag Alphabet — all 26 ICS/NATO signal flags plus number pennants 0–9 with Morse code and maritime meaning.
• Sound Signals — manoeuvring, fog and anchor signals per COLREGs as dot-dash patterns; tap any signal to hear it (horn, bell, gong — short 1 s, prolonged 4 s as at sea).
• Navigation Lights & Shapes — night light diagrams and day shapes per COLREGS for power vessels, sailing vessels, fishing vessels, towing and distress signals.
• Radio Call Templates (GMDSS/SRC) — 9 complete templates: MAYDAY, MAYDAY RELAY, MAYDAY acknowledgement, radio silence (SILENCE MAYDAY), end distress traffic (SILENCE FINI), cancel false alert, PAN PAN, PAN PAN MEDICO and SÉCURITÉ. All distress calls on Channel 16 — send DSC alert on Channel 70 first.

During a passage the app automatically logs when you pass a named seamark — lighthouses, beacons and named buoys. Unnamed minor buoys are deliberately ignored.

The entry is created at the closest point of approach („abeam“) and states distance and side (port/starboard), e.g. „⚓︎ Lighthouse ‚Bülk‘ abeam starboard — 2.3 nm“. Lighthouses are detected up to ~4 nm, buoys up to ~0.5 nm — matching how close you actually pass.

Toggle under Settings → Tracking & Log → ‚Auto-log seamarks‘. Data (from OpenStreetMap/OpenSeaMap) is loaded for the area at passage start and stored permanently — logging then works offline too. Without internet and without stored data, only a gentle hint appears, no error.

⚠️ Free community data, not official charts — do not use for navigation.

If the app crashes or hangs, iOS stores a technical report at the next launch. You find it under Settings → Info & Tools → Diagnostics. From there, mail it to the developer via the share icon — nothing leaves your device automatically, there is no tracking. Reports can be deleted with a swipe.

In the Area tab, the 'Weather' segment now also shows the official water levels (gauges) and the marine forecast for your surroundings — where available for your area. Dutch gauges are given relative to NAP (with sign), German ones relative to the local gauge datum. The marine forecast comes from the DWD or a weather model.

Area knowledge: Under 'More → Info & Tools → Cruising guides' you'll find guides for your cruising area — e.g. the Staande Mastroute through the Netherlands, the Baltic protected areas and the 'Crews' harbours'. They open directly in the app and are expanded continuously.

Harbour search: Under 'More → Info & Tools → Harbour search' you search the harbour directory (marinas and harbours from OpenStreetMap) or find harbours near you. The detail pages show aerial image, facilities, weather and wind shelter, AIS and community depths. New: The harbour search itself stays free — with Rubberduck Premium you save the visible map area offline via the ⤓ button at the top of the map (harbours, detail pages and map tiles); the search then works without internet and updates automatically when online.

⚠️ Water levels, marine weather and guides come via kielwasser.blog and are a planning aid — not an official source for navigation.

Under Ship → Inventory you manage four areas: inventory (permanent equipment), consumables (provisions etc. — with best-before dates), safety equipment (with inspection/expiry dates — life jackets, extinguishers, flares) and spare parts. The filter on top switches between all, inventory and consumables.

Structure: rooms and storage places (box, cabinet, compartment …) are defined under Settings → Ships → your ship → 'Stowage & deck plan'. Rooms live as sections on the deck plan: choose row (bow → stern), width (full/port/starboard), a span across rows and an L-extension in the editor. Two levels — below deck and on deck — even cover the lazarette above the cabin. Storage places appear as small chips inside their rooms (position port/centre/starboard).

Items carry quantity, unit, category, storage place and a photo (camera or library); consumables also a best-before date. With a target stock the inventory becomes a checklist — the alert bar shows what's due, and you share the procurement list from there.

Spare parts use the same storage places and can carry photos; maintenance items of the safety category link to an inventory item — the storage place comes along.

Web editor: in your Kielwasser cockpit (📦 Inventory) you maintain everything comfortably on your computer. The app picks up web changes when you open the inventory — pull down the list to force an immediate sync. Everything also syncs via iCloud.

During an active voyage the app checks the official notices at your position every 30 minutes. If a new closure appears in your area, you get a notification — even with the screen locked.

⚠️ A planning aid, not an official source for navigation.

Under More → Celestial navigation you work up a sun sight like with almanac and tables — without needing either: enter sextant altitude (degrees + minutes), lower/upper limb, index correction, height of eye and DR position; the app returns GHA, declination, observed and computed altitude, azimuth and intercept (Marcq St. Hilaire). Ephemerides are computed fully offline — meant as a backup when GPS is jammed, and for practice.

Two sights taken close together give a fix: keep the first LOP, enter the second sight, tap 'Fix from both LOPs'.

No sextant aboard? 'Measure with camera' photographs sun and horizon in ONE frame — tap the sun's center and the horizon, the app derives the altitude from the camera geometry and fills in the sight incl. exposure time (never look directly at the sun).

⚠️ Emergency and training tool — ±2–5 nm depending on sight quality.

Under Tools → Barometer you see the current air pressure — preferably from the NMEA network (MDA sentence), otherwise from the iPhone's pressure sensor. The app measures continuously (every 30 min by default, adjustable under Settings → Tracking & Log) and shows the 3-hour tendency with a trend graph (current passage or since app start).

Storm warning: if pressure drops sharply within 3 hours, the app warns you — a yellow pre-warning from about 4 hPa/3h, a red storm alarm from about 6 hPa/3h (thresholds adjustable in Settings). The storm alarm shows a red banner, sounds a siren (bypassing the silent switch) and wakes you with a notification — even inside the anchor watch. Tap 'Acknowledge' to confirm.

Barometer readings are also logged in the passage log: at passage start, continuously at the interval, and at passage end.

⚠️ A barometer trend is an early-warning hint, not a substitute for the official marine weather forecast.

The night-watch timer under Tools makes sure the helmsman on watch stays awake. You choose an interval from 5 to 30 minutes (in 5-minute steps). After each interval you must press a confirmation button — its position on the screen changes every time, so a mere reflex isn't enough and it's truly ensured that you're awake.

If you don't confirm in time, a pre-warning sounds first and then the alarm: a siren (bypassing the silent switch) plus a notification that wakes the screen. If the on-board alarm link is active, the alarm also rings on the other iPhones on board — waking the rest of the crew too.

⚠️ A wakefulness aid, not a substitute for good watch-keeping and lookout.

The on-board alarm link makes anchor, storm and dead-man alarms ring on the iPhones on board at once — without internet. The devices connect locally over Wi-Fi and Bluetooth (peer-to-peer), so it works far offshore with no reception too.

When one device triggers an alarm, a red banner with siren and a waking notification appears on the others; each person taps 'Acknowledge' for their own device. Turn it on or off under Settings → Tracking & Log → 'On-board alarm link'.

Watch link: as long as a watch is running on any device (anchor or night watch), all connected devices automatically stay awake — then the alarm reaches them even with the screen off. Important: the devices must be active / app open when the watch starts to enter this mode (after that they can go in your pocket). It uses a little more battery and ends automatically with the watch.

Honest limit: if NO watch is active and a device sits passively asleep (screen off), it can't be woken from outside offline — then the loud siren on the triggering device is the alarm. Every participating device needs the Rubberduck app and must be within range (near the ship).

⚠️ A convenience/wakefulness feature for the near range, not a safety or marine radio.

GPS Integrity warns you when your GPS position becomes unreliable — from a jammer (jamming) or deliberate manipulation (spoofing). Both occur for real in some sea areas (e.g. the Baltic, the eastern Mediterranean).

Turn on: Tools → GPS Integrity → enable. Premium feature. Monitoring runs automatically while a passage is active.

States (colour-coded): Green = reliable (silent). Yellow = anomaly (being watched, silent). Orange = disturbed — alarm sound and notification; don't rely on GPS alone, check your position against sea marks, compass and surroundings. Red = not trustworthy — continuous alarm; navigate by visual bearings and dead reckoning (compass + log), the last trusted position is in the logbook.

Why? Tap the status card: you see which checks triggered, with readings (signal strength C/N0, HDOP, position jump, time offset, dead-reckoning divergence).

Device GPS or NMEA: The feature already works with the iPhone GPS alone (accuracy, position jumps, motion cross-check). With a connected NMEA system (e.g. WLN10) it checks deeper: satellite signal strength (C/N0 profile), precision values (HDOP), time offset and dead reckoning from log and compass. A normal small difference between device and NMEA position is expected and does not trigger an alarm.

Settings: sensitivity (low/normal/high), own alarm sound on/off, and 'only warn at sea' (suppresses false alarms on land / in harbour). Anomalies are written to the logbook — on state change and periodically at the log interval set under Settings → Tracking & Log; a red state is always logged densely.

⚠️ A warning aid, not a substitute for attentive navigation and cross bearings.

The first time you open the app, a short assistant guides you: you create your ship and skipper, and can optionally connect your Kielwasser account right away (or later in Settings). If you're updating and already have a ship, you won't see the assistant.

Feature tour: A guided walkthrough shows you the main areas right inside the app — Trips & logbook, Ship, Cruising area and Anchor watch. You can restart the tour any time from the 'More' tab via 'Feature Tour'. Premium features are only mentioned there and point you to the subscription or this manual.

Manual always at hand: Every screen shows a book icon at the top. Tapping it opens this manual right at the section matching the current screen — e.g. the Ship tab opens 'Ship management', the Cruising-area tab opens 'Tides, weather & news'. That way you get help exactly where you are.