-- Last Updated: Nov-01-12 4:10 PM EST --
I have used one Garmin GPSMAP 76/78 series GPS since 2004 in all my vehicles, on all my canoe trips, and on all my hikes.
I clip it into a beanbag dashboard mount in the vehicles and into auto mounts glued on the thwarts or knee wells of my canoes.
My newer version, the 78sc, has pre-loaded coastal charts for the entire US, plus road maps and topo maps for the eastern half of the US loaded into the fixed internal memory plus a memory card. I also have downloaded satellite maps.
No, it's doesn't "talk" when operating in road route mode; it beeps. No, the screen isn't as big as a dedicated or built-in auto GPS. But the screen is plenty big enough to do the the job.
It has routed me all over the roads of North America for 8 years, and is especially useful in navigating around the greater NYC labyrinth. I just stick it in the glove box when parked in high crime areas.
I like the Garmin 78 series because it is waterproof and floats, and has many advanced features, and has push buttons instead of a gimmicky (to me) touch screen. But there are many other waterproof hand units that can can be used in vehicle, boat and trail -- though not many others float.