A remembered dream

A room half filled with a wall of water, the other half filled with air and no divide in between. Fishes swimming in the water, around head height. I can seemingly move between the two without difficulty or affecting the division. I can hear the fishes wondering what happens if they swim through the water out into the air. One does. I quickly move it back into the water. It swims away, then another three fling themselves out into the air...