The Bug

When falling from somewhere or moving the boat horizontally(on ice) while riding a boat, when you exit very quickly right before you hit blocks or liquids, the boat is in a different position in the client and server. The boat "lags" through the blocks but the rubber-bands back after a bit, unless the boat falls into water. If the boat is left above water right before hitting the water, then the boat will be stuck midair/float underwater for the client. When the client relogs then the boat is where it should be.

How to Reproduce

1. Place a boat high above water
2. Go into the boat and while in the boat fall into the water
3. Get out of the boat right before hitting the water
4. Repeat until timed successfully