SeaBase

Less apps. More sailing.

Seabase is the offline-first sailing companion. Anchor alarm, offline nautical charts, GPS navigation, tides, and a logbook — every tool you need on the water, all working without a signal. No accounts. No ads.

PAY ONCE
Seabase is a paid app — a single one-time purchase, and it's yours forever. No subscription, nothing auto-renews, no in-app purchases, no ads. Every offline chart region offered is included with unlimited downloads. You pay once and get the whole app.

ANCHOR ALARM
Drop a virtual anchor and Seabase watches your position with phase-based drift detection — scope warnings, drift alerts, and critical alarms with sound and vibration. A sliding-window filter rides out GPS noise instead of waking you for it. Arm it after the fact with "Already Anchored" mode, pause and resume on the fly, and control the whole watch from your wrist. Replay any past anchor session on a scrubbable radar track. Built to wake you before your boat does.

OFFLINE CHARTS
Download nautical chart regions to your phone with OpenSeaMap seamarks built in. A global base layer keeps you covered when you sail past your downloaded zone. NOAA depth overlays for US waters when online and offline (with map download).

GPS NAVIGATION
Long-press the chart to plan a route — built-in land detection flags legs that cross land. Live navigation gives you bearing, distance, ETA, cross-track error, and remaining distance with heading-up auto-rotation. Save routes and replay them. A dedicated GPS Navigator adds a radar HUD plus point-to-point go-to.

TIDES
3,500+ tide stations worldwide, completely offline. NOAA-accurate harmonic prediction from a bundled database — no API call, no signal needed. A clear "now" hero card with a trend chart and high/low times.

NEARBY PLACES
An offline harbor and anchorage finder covering 25 cruising regions worldwide — marinas, fuel docks, pump-outs, ramps, and more — with a searchable list and an offline map view. Hand off any place straight to the GPS Navigator.

LOGBOOK
Auto-tracking trip recorder with idle detection, photos, notes, and a speed graph. Shareable trip cards with a route preview. CSV export. Sail Recap turns any recorded trip into a shareable highlight video.

REFERENCE
Knots with animations · COLREGS rules · NATO phonetic alphabet · Safety-equipment guide (US, EU, AU, UK) · VHF MAYDAY / PAN PAN / SÉCURITÉ guide · IALA buoyage.

EMERGENCY
Always-light emergency screen so it works at bright sunlight. Heave-to guide, quick-reference distress procedures, MOB tracker, and rescue contacts.

PRIVACY
Your trips, photos, and routes never leave your phone, and your GPS position is never sent anywhere. The only network calls are to map/chart tile hosts for first-time region downloads. No accounts, no analytics, no tracking.

LICENSE
Recreational use only. Not a substitute for professional navigation equipment, official charts, or sailing certifications. You are responsible for your safety on the water.

Built by sailors. Yeoman Ventures LLC, California.
www.seabase.app · gosailing@seabase.app