The reason behind all this is that fish are much better at swimming forward than in any other direction. They also need some velocity to make a turn. In that sense fish are like higher dimensional cars. Now stir some bumping into each other and colliding with terrain into the mix. Add a pinch of non-uniform drag and two scoops of underwater currents. Now you got yourself a real problem at hand. Enjoy!
Posted by Jonas 8 years ago