XOG can use Lowrance fishing and marine maps. It records tracks and can use straight-line, point-to-point navigation. I think you could simply mark a single point like a fishing spot using the cursor to add it to the address book.
For external power you can use an aftermarket USB battery pack with four AA batteries.
Its screen visibility is about average, meaning not so good in bright sun...I haven't seen an under $500 touch-screen GPS that is has good visiblity in direct bright sun. XOG is weatherproof either.
Though you didn't ask, this GPSr is a killer GPSr !! It's the one I've been waiting for. The ability to load detailed USGS topo maps and satellite imagery from Lowrance Mapselect just blows everyone away, especially for under $250. That being said, if your Dad doesn't want or need the auto-nav street routing for in the car, he'd be better getting a handheld or fishing GPSr model.