OpenWater - Water Speed

openWater is a GPS speed and technique tracker for wingfoiling, parawinging, downwinding, windsurfing, kitesurfing and sailing. It is open source, works entirely offline, and never asks you to create an account.

RECORD ON YOUR WATCH OR YOUR PHONE

Start a session in one tap. The Apple Watch app runs standalone — it does not need your phone nearby, or even installed. Water Lock engages automatically, and the session keeps recording with the screen off and your wrist down. Your track is written to disk continuously, so a flat battery or a crash costs you seconds, not your session.

Seven live screens: speed, splits, session totals, wind angles, foil time, controls, and a racing start countdown you can sync to the committee boat's gun.

SPEED, MEASURED PROPERLY

Every category the speedsurfing community actually uses:

• 2 second peak • Best 10 seconds, and the average of your 5 best 10-second runs • 100 m, 250 m, 500 m, 1 km, 2 km, nautical mile, 5 km, 10 km • Alpha 500 — a 500 m run with a gybe, finishing within 50 m of its start • 30 minute and 1 hour averages • Any custom distance you add, applied retroactively to sessions you already recorded

These are computed on the continuous track rather than snapped to the nearest GPS fix, because a single second of slop is ten metres at twenty knots. Speed comes from the receiver's Doppler measurement, not from differencing positions.

SEE WHAT ACTUALLY HAPPENED

An hour of winging in a bay is forty passes through the same water, and drawn as one line it is unreadable. openWater fixes that:

• Flights are drawn bold, slow sections fade back, falls get a marker • Pick any single run and the other thirty-nine drop away • The Runs view drops the map entirely — one lane per run, stacked in time, so nothing overlaps. It reads top to bottom like a score. • Replay the whole session with a playhead, speed heatmap and live readout

FOR FOILERS

• Time on foil, number of flights, longest flight, takeoff speed • How long your pump-up takes • Falls counted separately from touchdowns, because they are not the same thing • Longest clean run — the metric that keeps improving long after top speed stops

FOR WING AND PARAWING

• Wind direction worked out from your own track, with no weather service and no internet needed • Polar curve, VMG upwind and downwind, tacking and gybing angles • Gybes and tacks detected and scored: entry speed, minimum speed, recovery time, and whether you stayed on the foil • Port versus starboard comparison, so you can see the side you have been quietly avoiding

FOR DOWNWINDING

• Glides detected from the pump-and-glide rhythm • Glide count, longest glide, and what share of the run was on foil • How often you linked to the next glide without dropping • The swell period you were riding

YOUR DATA IS YOURS

• Import GPX, TCX, FIT and CSV — Garmin, Coros, Suunto and most apps • Export GPX, TCX, CSV, GeoJSON, or a complete lossless archive • No account, no server, no tracking. Nothing leaves your device unless you send it. • Sharing trims the start and end of your track by default, because those are usually your car or your home