I've been using the Garmin "GPS72" for over a year now and really happy
with it. It was low cost (under $100), designed for marine use with
all the navigation markers needed to cruise the Florida (or any other)
waters. It's also simple to use and can be programed to show what you
like to see for your personel usage. It is waterproof with an external
connector for boat battery power. If you decide to mount it at the
helm it has a quick disconnect type bracket that allows removal but
keeps it in place during heavy weather.

Mike, Pensacola, FL.