[javajosh]

> it is surprisingly easy for even a well-intentioned skipper to drift out of a legal fishing zone while tending to everything else happening on the boat

Skippers do have a lot to deal with, but I don't think it's asking too much of them to have accurate awareness and control of the position of their craft at all times.

If staying out of forbidden areas is difficult, then perhaps one could use a geofencing app that would work offline using GPS signals, which are generally easy to pick up on the water in good weather. You would input some boundary on a map, and the app will periodically check position and alarm if you've entered the forbidden area. I bet this is even a feature on marine navigation systems and even some watches.