Landlubber: Dive Navigation

Brief it, slate it, swim it in the fog — then see the track you actually swam laid over the plan.

Underwater navigation is the one dive skill that gives you no feedback. You swim a square, surface forty metres from the shot line, and neither you nor your instructor can say which leg went wrong.

Landlubber gives you the feedback twice: once on dry land, where the drill can be watched, and once underwater, where it has to be swum.

ON LAND Walk the pattern with your phone as referee. It reads your heading, counts your steps, and afterwards draws the shape you actually walked against the shape you meant to. Indoors a corridor is enough. Outdoors it takes a fix and measures how far you finished from where you started.

IN THE WATER Five dive sites you brief, slate and swim. Study the chart on the boat, choose what goes on your slate, pick the visibility and the current — then the chart is gone and you have the compass, the count, and whatever you wrote down. The reckoning afterwards lays your track over the plan.

One of the sites is the real thing: the El Aguila, a freighter sunk off Roatan and broken into three by a hurricane, from a photogrammetry survey of the wreck where it lies.

THE INSTRUMENT A working dive compass in three dimensions. Turn it in your hands, tap any part, and read why it earns its place on a dive. Turn the bezel with two fingers, exactly as you would underwater, and feel it click.

ONE CAGE, ALL DIVE Set the bezel so N sits caged between the two index markers. From then on you never read a number again — you keep a graduation in that cage. N going out, S coming home, N, E, S, W round a square, without touching the bezel at any corner.

THE PATTERNS, WALKED AND SWUM • Reciprocal — out on a heading, back on its opposite • Square — four legs, four right turns, back to the start • Triangle — three equal legs and 120-degree turns • U-pattern — long lanes and short hops, mowing an area • Expanding square — legs growing by a pair, out from a datum

SEARCHES Two of the dives hide something. A camera slipped somewhere near a datum block; a marker buoy went over the side onto a wreck's deck. Both land somewhere new every time, so the pattern is what finds them, not your memory of where it was last dive.

TUTOR AND EXAM Tutor shows every number and ticks on each step it sees. Exam hides them and asks you to commit your own count before the reveal.

WHAT IT WILL NOT DO It is not a substitute for water time. Buoyancy, trim, gas, task loading and a real buddy are absent here, and they are most of what makes navigation hard. What it replaces is the guesswork in the debrief.

Made by a technical diving instructor. No accounts, no tracking, nothing leaves your phone.

Free: the instrument, the reciprocal drill complete, and the house reef dive. One optional purchase opens the rest of the ladder, on land and underwater. Paid once, no subscription.