I have experienced this several times since the update. I had previous created a boat and leave it on a sea. Then go underground where I travel through a mine a "significant" distance (the mine is under the sea). Suddenly I teleport above ground into a boat.
Steps to duplicate (it's good to start fresh when testing.)
-Start a creative world.
-Get into a boat.
-Use the boat a little.
-Leave the boat for a while.
Reopen your game. You will then be teleported into the boat you left earlier.