A dive instructor on your wrist.
Every dive computer shows you 18 metres. Wetskin tells you to level off. It reads depth, time and tissue loading like any computer, then says what an instructor would say about it — in four words, at the moment it matters.
Depth
18.4m
No deco
8min
Dive time
24:10
Max
19.2 m
Temp
24°C
Slow Down
Ascending at 15 m/min. Keep it under 9 m/min.
Design preview, not a screenshot — the app is still being built.
The instructor layer
Numbers don't coach. Sentences do.
A dive computer that says 15 m/min has told you the truth and nothing useful. Wetskin keeps the number and adds the instruction. Every alarm is short enough to read at a glance, phrased as an action, and never contradicts the algorithm underneath.
Slow Down
Ascending at 15 m/min. Keep it under 9 m/min.
Depth 30 m
Level off here. Stay shallower than 40 m.
NDL Low
5 min of no-deco time left. Begin your ascent.
Too Deep
Past 36 m. Ascend slowly now. Watch is rated to 40 m.
Deco Required
Mandatory stop at 6 m. Do not surface.
High ppO₂
Above 1.4 on EAN32. Ascend or switch gas.
Yellow warns once. Red repeats every ten seconds until you act on it. Depth alarms are yours to set, so the numbers above are examples, not fixed limits.
Through the dive
It talks when an instructor would.
| Moment | What an instructor says | What Wetskin does |
|---|---|---|
| Before you get in | Did you do your buddy check? | Pre-dive checklist, gas and MOD confirmation, plan summary |
| Descent | Equalise. Slow down. | Descent-rate nudge and an equalise reminder through the first 10 m |
| On the bottom | Watch your depth and your air. | Plan-depth ceiling, NDL countdown, turn-pressure reminder from your own gas use |
| Ascent | Slow down. | Ascent-rate bar with haptics, and the Slow Down alarm when you ignore it |
| Safety stop | Hold 5 m for three minutes. | Guided stop that counts down and warns when you drift off depth |
| Back on the boat | Here's what to fix next time. | iPhone debrief: ascent control, stop held, depth discipline, air use, one tip |
| Over a season | You're getting better at this. | Skill trends across dives — buoyancy at the stop, ascent control, SAC |
Underneath the sentences
A real dive computer, not a reminder app.
Bühlmann ZHL-16C
Sixteen tissue compartments with gradient factors you set yourself — 40/85 to start, conservative or liberal as you prefer. No-decompression limit, stop depths, time to surface, and a tissue graph you can read mid-dive.
Air, nitrox, and the maths
Maximum operating depth and ppO₂ per gas, a high-ppO₂ alarm, CNS loading, and gas-switch prompts you answer with a button. Recreational dives lock the gas list so nothing changes by accident.
Depth, rate, heading, temperature
Depth and water temperature from the Ultra's own sensors, ascent rate as a bar you can read without counting, a compass you can set to a bearing, and your maximum depth kept in front of you.
Surfaced, and still working
Surface interval, desaturation, no-fly time, and the dive saved to Health as an underwater-diving workout with its depth and temperature samples.
Water Lock
Your hands never touch the glass.
Underwater, the Ultra's screen stops taking taps — that isn't a limitation to work around, it's the rule. Everything Wetskin does during a dive is reachable with the two controls that still work with cold, gloved hands.
- Digital Crown turns through the dive pages — main, compass, gases, dive info — and adjusts any value you're editing.
- Action button drops a bookmark, sets your bearing to the current heading, switches gas, and acknowledges an alarm.
- Haptics carry the alarms, because a screen you can't look at is a screen that can't warn you.
- Night mode drops the display to grey and dims it for dark water and night dives.
The iPhone side
The debrief is the point.
Wetskin's companion app plans the dive before you go in and takes it apart afterwards: depth profile, maximum, average, the gas you breathed, your gradient factors, every bookmark you dropped, and the entry point on a map.
- Surface air consumption from the end pressure you type in. Wetskin has no tank transmitter, and doesn't pretend to.
- A live view on the surface while your buddy is still down.
- Dive sites you build up over time, with how many dives and how deep.
- Your gear: cylinders, start pressure, average SAC, algorithm, gradient factors, alarms, units.
Plainly
What Wetskin isn't.
A dive computer is life-safety equipment, and this one isn't finished. Here is the honest state of it, so you can decide whether to follow along.
It is not a substitute for training
“A dive instructor on your wrist” is how it behaves, not what it replaces. Wetskin is a dive aid for certified divers. It cannot see you, it cannot check your buddy, and it is no reason to dive beyond what you were trained to do.
It is not your only computer
Dive with a second, established computer. Wetskin will say so during onboarding, and it will say so here.
It is not released
There is no download and no App Store listing yet. Reading depth underwater needs an entitlement Apple grants dive apps on request, after review; development access comes first and shipping is a second approval. Everything on this page is in the plan, not in your hands.
It is not certified
No EN 13319 testing has been done. If that changes, this page will say which laboratory did it rather than implying it.
It is not for decompression diving yet
Version one is recreational, no-stop diving. The deco stops, gas switching and 40/85 gradient factors are designed and will ship behind a setting you turn on deliberately, after the recreational version has real water behind it.
It stops being a gauge past 40 m
That is the Apple Watch Ultra's rated depth, not a choice. Wetskin warns you well before it and will not quietly show you numbers it can't stand behind.
Who's building it
An instructor who writes software.
Wetskin is built by Norstride's founder: an active SDI scuba instructor with more than thirty years of diving and over a thousand logged dives, teaching new and experienced divers every week. Teaching is where the idea came from — rapid ascents, skipped safety stops, confusion about no-decompression limits, alarms ignored because nobody explained what they meant.
The other half is thirty years of software engineering, ten of them building FDA-regulated systems for medical-device manufacturing under ISO 13485 design controls, where software that loses data or shows a stale number is a defect, not an inconvenience. A dive computer deserves the same discipline: every failure listed with its effect on the diver, every dive sample written to disk as it happens, and a loud, haptic failure rather than a confident wrong answer.
Wetskin is in development by Norstride Inc. and is not currently available. Nothing on this page is a dive table, a dive plan, or dive instruction. Diving carries risk of serious injury and death; dive within your certification, with a buddy, and with a second dive computer.
Apple, Apple Watch, Apple Watch Ultra, iPhone and App Store are trademarks of Apple Inc. SDI is a trademark of Scuba Diving International; the instructor credential above is the author's own and implies no endorsement of Wetskin by any training agency. Wetskin is not affiliated with these organisations.