If I ever wind up getting a tin boat and using the rivers near my house I'd like a GPS device to show me approx. where I'm at. Is there any real reason when using rivers to get a marine exclusive GPS, I just need to see land masses and bodies of water so I knowhow far from home I've ventured. Pretty much any GPS can do that I'm thinking. What do you say, marine due to being on the water? Or other reasons for one?