What do sharks use for buoyancy?
Sharks employ a number of mechanisms to maintain their position in the water column, one is physiological in the form of an enlarged liver with a large oil content. The other ways are morphological. The pectoral fins are aerofoils (like the wings of a plane), being convexly curved on the dorsal side and flat or concave on the ventral side. As the water moves across the fin the water particles move faster and are spread further apart on the dorsal side which results in the water moving over the top of the fin to have a higher pressure than the water below, water (and air) moves from areas of low pressure to high, and so the water under the fin moves upwards, pushing the fin up. This is enhanced but the upwardly pointed snout. The other mechanism work to push the tail upwards.
