Garmin makes good equipment, but I am partial to Lowrance for marine applications. If you want a hand held unit, you may want to consider a Lowrance Ifinder H2O. This is a nice unit and works well with both Lowrance's hotspot fishing pro map card or navionics and it is very water proof.
If you want a unit that gives you turn by turn directions in the car and can be used for marine applications as well, I would suggest the Lowrance XOG. It is water resistant, but not submergable like the H2O unit. I just bought one of these units and I love it. It is a little more confusing to use than my Garmin GPS for the car, but it is an excellent all around unit. Best of all, you can get it from Bass Pro right now for $159. 6 months ago it was around $279. Good luck!