What is the substance of a shark skeleton?

A shark's skeleton is primarily made of cartilage, which is a flexible and lightweight tissue. Unlike bony fish, sharks do not have bones; instead, their cartilaginous structure provides both strength and agility in the water. This composition allows sharks to be more buoyant and reduces their overall weight, aiding in efficient swimming. The cartilage is reinforced with structures such as calcified areas, giving some parts of the skeleton additional support.