you have choices.
- you can restore the world file, and your boat will be where you left it, assuming it was not in materials on your person. This undoes all your exploration and world edits including changes to chest contents since the save file selected (usually you want the next to last, the .old one).
- you can restore your person file, if the boat were in your bag.
- you can cheat in another boat.
- if well established, you can eat the loss and just keep going.
- the boat may be where you left it. you could attempt a raft-recovery.

its a good idea to force a save at key points if you have stability issues. You can do that by logging out, but the menus changed, I don't know if there is a better way now. Like if you are about to take a boat ride, or collected ore for 2 hours ... force that save. And, if not already, keep backups.