Obviously viewability in direct sunlight and some level of water resistance are the most important attributes. Don't really need turn-by-turn navigation, but at a scrolling overhead map-type view with streets names and numbers would be important.  Topo maps for the lakes aren't a necessity either. I don't want to spend more than a couple hundred $. I've tried using a bunch of different phones and they all suck in direct sunlight no matter how high you turn them up.