Just run a search on handheld GPS im sure it'll turn up quite a few threads.
If i were you i'd have a look at the Garmin GPS 72 or if you have more money then the Garmin GPSmap 72. Quality units, quite large though, but they are completly waterproof and float.
Has anyone had any experience with the Magellan Marine GPS. I was on their stand at the boatshow and the unit looked really tough with maps and navigation information. Similar price to the Garmin GPSMAP 76.
I personally prefer Garmin. I prefer the GPS 12 model or higher. The e-trex is great as a standby h/h gps but can be a bit fiddly for ofunctions other than the basic Lat/Lon.
I have a refurbished garmin 12 for 3 years. Cost me £90 from one of the Web traders. Easy to use, eats batteries (came with rechargeables, but I always keep a spare set of standard alkalines on board also).
I use a secondhand Garmin GPS III Pilot. Paid £150 three years ago & it is great. I use it in my vehicle (Jeep) whilst offroad driving, in handheld mode for hiking & now on my boat. I cannot fault it!