While in high tide inside the boat at Riffy water was above half of one of the northern cargo holds and after walking back onto the water from the floor to get to the stairs I slid across to the wall and slid back when I tried to move. When I was on the water I could only make one step from a stand still and once I started sliding I couldn't make my character move in till I got back to the floor or hit the wall. This didn't happen every time I attempted walking into the water. I assume this is caused by the boat not being a land mass/not interacting with the water and allowing it to be phased through the floor.