Funny, I was looking for a gps unit to put on front of my boat just prior to pulling up crappie.com. The units can be linked together for your info. Here is an article about WAAS which says that WAAS will get you within 3 meters where regular GPS will get you within 15 meters. For the gentleman who stated that his spot was on land this may explain why!
Garmin: What is WAAS?