I'm currently building an Atlantic and I've spawned in various different aquatic mobs but not long after I've spawned them they start ramming into walls. They just swim in the direction of a wall forever like they think they can get through. I think it has something to do with pathfinding where it can't sense the block in front and maybe has locked that direction accidentally. It's really annoying as it ruins the look of my build. This problem occurs with every aquatic mob. It would be great if you could sort this out.