How about creating a wristpod that can fit under the watch in the same way the chargingclip does?
This would make it possible for swimmers to log strokes and how many lengths/laps you've been swimming when exercising in swimmingpools. I assume it would be possible with an acceleratorpod and good algorithms to part strokes from turns due to gliding and/or dip'n'roll when turning. By entering the length of the pool you could for instance keep instant track on how far you've been swimming.
I'm not sure if physical transmission between clip and watch works under water. If it does it would be great but even if it doesn't I assume normal wireless contact would work. I know that transmission in water is more difficult than on land but when the devices is next to each other this can't really be a problem. If the pod could be easily moved from wrist to foot it could then be of good use for triathletes when switching over from swimming to cycling. The pod could hopefully also be used for other sports like wheelchairracing, rowing, kayaking and crosscountryskiing if algorithms are finetuned. Maybe even boxing to measure speed and explosivity if that is interesting.
This does of course pose new challenges for sports training gym but that's just a matter of work.
May you all have a nice midsummerweekend!