You know GPS units are handy in the woods ("Satellite Hiker," April 2004). But they also work wonders on water. You can:
Travel through fog or darkness. Before GPS, low visibility left paddlers with two choices: stick close to shore or take a rest day. With GPS, you can pick a route and follow the pointer past rocky peninsulas and other hazards.
Find a channel in a maze of many. Punch in the map coordinates before leaving home, and GPS will eliminate the guesswork.
Determine the shortest way. Hug the shore or cut across deep waters? If you plot a digital track, you won't waste time navigating through islands or across big lakes.
Remember favorite fishing holes. A waypoint on open water is like having a buoy that never moves.
Put information at your fingertips. Many units provide sunrise/sunset times and regional current and tide data. Some upload marine topos.
Estimate time and distance. GPS provides up-to-the-minute progress reports that let you know whether you can outrun storms and darkness.