“Crazy Lenny” the Mad Mariner has stress tested a few portable GPS and VHF handhelds: the Garmin GPSmap 76c, the Lowrance iFinder H2O, the Raymarine Ray 101, the Uniden Voyager, and the Uniden MHS 350.
How were they stress tested? dropped them a few times, tossed them around in a cooler of ice and live fish, threw them overboard into a couple of feet of salt water, drove a trailer and boat over them, handed them to a bunch of kids with instructions to break them, and then finally flushed then down the toilet.
A week later he tested them and they all still worked.
(full review at madmariner)