A mirror?

In a studio with grey walls and wooden floors, a man in a grey shirt crouches low to the ground, then crawls forward on his hands and knees while another man films him with a camera on a stabilizing rig; the crawling man moves across the floor toward a doorway where a third man stands, and the camera operator follows them as they walk through the doorway. The scene cuts to an underwater shot of a large, pale fish with a rounded body and a small, dark eye, which slowly turns its head to face the camera.