O. scyllarus, particularly nearing a molt will occasionally spook and swim up into the water column to escape. They can reach speeds approaching a meter per second. When you are living at 20 meters, that is no problem. When you are in 50 cm of water and hit the surface, you keep on going - sometimes right out of the tank. We keep some sort of lid or netting on all of our Odontodactylus tanks and lab assistants are instructed to be extra careful when working on containers and aquaria housing them. For a large O. scyllarus, a five foot drop onto a epoxy floor is often fatal.
Roy