OnsetHOBO MX2203 TidbiT 400ft Waterproof Temperature Data Logger

This thermometer worked for several years without any problem.

I had to return the first one and replace it because it leaked and failed. Specs indicate 400 foot max depth but the seal failed when used for about a half hour at depths up to about 350 feet. A new one survived at around 300 feet, the only test so far. Inspection of the construction makes me uncertain whether it could withstand its maximum depth specs over the long term. Features, however, are very useful for data recording, logging, graphing, etc. The user interface can be a little cumbersome but quite extensive in settings and options.