Excellent! Good luck debugging your things in the water. If your hardware works when out of the water no matter how long you run it, and then it reliably stops working once you put it in the water, then that points to a likely mechanical issue where you need to seal and protect things better.
One helpful troubleshooting tip is to use bm_fprintf (v0.12 and earlier) or spotter_log (latest, upcoming in v0.13) to write logs to Spotter’s SD card periodically, for example once every minute, run a long dry test, like overnight, and then check the logs. Then run a similar test in the water and check the logs.
You might also find some inspiration or tips in this topic on a camera project: Underwater RPi Camera Build