I use a Garmin GPS72 handheld. There still may be a few around but they have been replaced with the GPS76 series. Here's a place to start reading up
http://www.garmin.com/marine/products.html#handheld
You can really get a bunch of bells and whistles that start driving up the price. However, all you really need is a basic GPS with WAAS (wide area augmentation system). It is the mapping screen (even without Mapsource to show details) that will show you your present position in relation to your saved waypoints within a specified distance that allows you to relocate your fishing spots quickly. As you get closer to the waypoint you begin to zoom in and the WAAS will put you right on it instead of just the general area.
I also suggest you purchase a D/C cable and a Data Cable. You can really go through the batteries and with the data cable you can download your GPS. Always need a backup. It's not fun loosing all your coordinates and starting all over. You will need software to communicate with the unit to download. Here a freeware the works well.
http://www.easygps.com/