| Locomotion |
Sharks swim by moving their back fin from side to side in a sweeping motion, which propels them forward. The large upper lobe of the back bin (also known as the caudal fin) of most sharks provides most of the forward thrust-like movement. Sharks, also have a well-developed lower back (caudal) fin lobe for greater thrust. As a shark moves through the water, it angles the pectoral fins to change its direction when desired.
Sharks are only slightly heavier than water, so they naturally, like humans, tend to sink. Buoyancy or a "lift" is provided in two ways. First, bull sharks store large quantities of oil in their liver (an extremely vital organ in marine based animals). Because oil is less dense than the water they're swimming in, storing this oil decreases the overall density of the shark, and increases its buoyancy. Second, as a shark swims, its pectoral fins provide lift. If a shark stops swimming it will sink, but its stored oil and relatively light skeleton help it to float and decreases the amount of energy that must be used up on swimming.
Sharks are only slightly heavier than water, so they naturally, like humans, tend to sink. Buoyancy or a "lift" is provided in two ways. First, bull sharks store large quantities of oil in their liver (an extremely vital organ in marine based animals). Because oil is less dense than the water they're swimming in, storing this oil decreases the overall density of the shark, and increases its buoyancy. Second, as a shark swims, its pectoral fins provide lift. If a shark stops swimming it will sink, but its stored oil and relatively light skeleton help it to float and decreases the amount of energy that must be used up on swimming.