Can I use the StenLight underwater?
Yes, but applying power to it for long periods of time will eventually electrochemically corrode the battery connector. This happens a lot faster in salt water (or in a washing machine) than it does in fresh water (minutes vs. hours). If you need to go through a sump or duck-under, just unplug the connector afterwards when it is convenient, shake the water out of each side and then plug them back in.