I use a Garmin 60CSx mapping GPS, and after re-setting the trip log before paddling I get Distance, average speed, Max speed. and Distance, Time & Bearing to next way point if I'm paddling a route. The 60's series of Mapping GPS are also splasp /waterproof.
I alway place the GPS in a flexiable drybag with clear windows, current I'm using the Sea to Summit waterproof TPU IPX8, with good success, they are handy as they have four attachment points. To beat condensation, I place a supper dry wettex sponge in the case cut to size, this will soak up any condensation and if there is a minor leak it will take care of it, since the sponge will change colour and swell if there is any moisture leakage, it acts as a early warning.