When driving the boats in multiplayer over waves, the boat goes deep under the water and then high out of the water on an arc of movement. Seems like the boat's movement are out of sync with the wave's physics and it goes too far under and out of the water with no particle effects like spray, etc.

Also when AI and real players board the boat some seating positions are way off the actual boat. I.E. the guy in the middle will be in a seated position but his butt is a meter off the boat so looks like he is floating