Another, much less expensive, option is an Eye-Fi card. This is a SD card with geotagging built into it. It works, but there are two problems with it. 1) It's slower than the newer SD cards. You will have to wait for pictures to save. 2) It doesn't work off of GPS, but off of an extensive data base of wi-fi connections. So if this lake is not near existing wi-fi connections, eye-fi won't help. In an urban area, it's fine.
The card has other benefits, if you want to take advantage of them, like automatically transfering the pictures to a laptop via wi-fi.