White Shark Projects has had the privilege of being able to record great white shark sightings in Gansbaai, South Africa since 1989. Being one of the largest predatory species of shark, it always amazes us how gracefully these sharks seem to glide past our cage diving vessel, Shark Team. With the recent sightings of some large 4.5 – 5 metre great white sharks in the bay…. It makes you wonder, how does such a huge animal keep a float?

Beautiful 4.5 metre female great white shark.

Buoyancy is the ability of an animal to float in the water. Sharks are slightly heavier than water, so they have methods to help maintain buoyancy and stop themselves sinking to the bottom of the ocean…

Great white sharks, like all sharks, lack a swim bladder filled with gas that bony fish possess to stop them from sinking. Instead, they rely on other anatomical adaptations such as the liver. A shark’s liver can make up to an incredible 25% of its total body mass. This huge liver is filled with a type of oil called squalene which has a low density making it lighter than water, therefore helping the shark maintain buoyancy.

Another method great white sharks use to stay afloat while in the sea is something called “dynamic lift”. This is where the shark uses its large pectoral fins which are situated on either side of its body to create lift beneath them – almost like the wings on a plane.

Great white shark showing off her pectoral fins and gliding like a plane.

In addition, a shark’s skeleton is made of cartilage which gives the animal a few advantages. Cartilage is strong, flexible and light, weighing about half the density of bone. This light skeleton greatly reduces the sharks body mass, also helping to prevent it from sinking.

So, these features are what make even the biggest sharks we see here in Gansbaai stay afloat while they are gracefully gliding past our cage diving vessel, Shark Team. We are truly lucky to see such wonderfully evolved ocean predators right on our doorstep.

Want to learn more about sharks? Read our previous blogs!

Photo taken from White Shark Projects cage diving vessel, Shark Team – by Tom Young from The Great Projects

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Written by Georgina Vermeulen
Marine Biologist at White Shark Projects

Published 4th November 2019