Device: Samsung Galaxy S 3 Mini (AT&T newer version)
How to reproduce:
Step 1: Make a world. Dig a ledge or find one.
Step 2: Somehow make/spawn a boat on the higher ledge.
Step 3: row your boat until its on the very edge of the blocks. It may or may not "drift/rotate" by its self even when not moving the boat manually.
If Step 3 doesn't work: Try this against a wall.
(NOTE: The rotation continues for a LONG time after you use the buttons to move the boat. Not a short one, but a CONTINUOUS ONE.)