The boat mechanics in this game are pretty bad. If you just nudge and island, or edge it on the beach to be able to jump dry, the fishing boat gets stuck on invisible terrain assets.

Any way to unstick a boat other than swim back to Wharf and recover?

Try to relog, sometimes it moves boat a bit

Change servers. It usually moves the boat out enough to get unstuck.

My boat got eaten in about 2 seconds because I sailed to what is evidently an unapproachable island.. The game teleported me to a nearby island, but left my boat in no mans land.. Escape moved me to a slightly closer island, but I've been swimming and running out of gas for last half hour. Super annoying.

I strongly suggest carrying a traveler's map when out at sea. Saves you from the long swim back if something should happen.