The Moving Fish

First let me state that the spiral is animated and moving by design. The spiral is not an optical illusion. That said let's see how we can transfer the animation from the moving spiral to the fish scene. Focus on the spiral center exclusively for at least 60 seconds, then shift your focus to the fish. It's amazing how the fish actually float in the ocean currents.

Update: I now know that this is Jerry Andrus' Tri-Zonal Space Warper. The original instructions were "Stare at the center of the spiral for about a minute. Then look at the back of your hand.It will appear to be twitching and moving."