In other instances, sharks are studied by photo identification on the Farallon Island, off the San Francisco coast. The Farallon Islands are a white shark hotspot due to large seal and sea lion populations. The observation can be made from the safety of dry land. On other occasions, a mini-camera was attached to a white shark. A bony fish only has one on each side.
Sharks have denticles instead of scales.
These can severely lacerate the skin of someone who is brushed by a shark. Sharks' teeth are replaced throughout their lives. Sharks lack airbladders that give bony fish buoyancy. That's why shark's liver is big and especially rich in oil, lightening its mass in the water. A shark's skeleton is made of tough but flexible cartilage.