When sailing in a boat, it sometimes strikes objects not near the boat. The boat may break and the wood bits appear several blocks away. Also, sometimes when exiting a boat, you can't hit it with an axe to pick it up. If you exit the game and re-enter, the boat is in a different place than it was shown before exiting. Then the boat can be struck and picked up.
This seems to be an issue on SMP. It's not stated here (that I saw) as to whether or not it was SSP or SMP, but I'm assuming the latter since I had this issue. It seems the client and server believe the boat is in two separate places.