Sharks And Buoyancy: Why Don’t Sharks Sink?

Sharks are a species of fish that live in the ocean but one of the many questions people have about sharks is why don’t they sink?

Sharks And Buoyancy: Why Don’t Sharks Sink?

Sharks are able to float due to buoyancy and their whole biology is adapted to increase and maintain their buoyancy, preventing them from sinking and allowing them to swim in many directions underwater.

Here we are going to be looking at a shark’s buoyancy and how they maintain it!

How Sharks Maintain Buoyancy?

Despite being fish, sharks don’t actually have swim bladders. Swim bladders are the organs fish use to maintain their buoyancy and prevent them from sinking.

These bladders are filled with air, allowing fish to maintain buoyancy – but sharks don’t have these organs.

Instead, they use three other important parts of their biology to maintain their buoyancy.

This prevents them from sinking to the bottom of the ocean without the need of a swim bladder.

These three components of a shark’s biology are their livers, their fins, and their skeletons.

Let’s take a look at each part of the shark’s biology in detail to see how it prevents them from sinking and helps them maintain buoyancy.


While most fish have swim bladders, the organ that sharks rely on to help maintain their buoyancy is their liver.

Most sharks have very light livers that are low in density and gravity, making it an ideal organ to use to maintain buoyancy.

This is because their livers are lighter than water itself. Not only that but the shark’s large yet light liver is filled with a type of natural oil that contains squalene.

Squalene is produced naturally by the shark and is very important to the shark’s health. It is also very light and thus, helps maintain buoyancy in the shark’s liver.


Another key component of a shark’s biology which helps maintain buoyancy is their fins.

Their fins help them achieve something called ‘dynamic lift’ which acts very similarly to a bird’s wings.

They create a lift which brings the shark upwards, preventing them from sinking down into the bottom of the sea.

The fins used to achieve this method are the shark’s pectoral fins, which can be found on both sides of its body under its belly.

The tail which features caudal fins are also used to help maintain buoyancy while thrusting the shark forward.

As a result, constant movement is needed for a shark to maintain its buoyancy.


The final part of a shark’s buoyancy which is vital to helping them maintain buoyancy is the skeleton.

A shark’s skeleton does not actually contain much bone, unlike our own.

This is because bones are much heavier than another kind of material that provides a similar purpose – cartilage.

As a result, most of a shark’s skeleton is actually made of cartilage. This reduces the shark’s weight and density by half, making them much lighter and thus more agile.

So, with a skeleton made from cartilage rather than bone, sharks are lighter and able to maintain their buoyancy with ease.

Final Thoughts

As you can see, sharks have adapted over time to improve their biology to help make maintaining buoyancy much easier.

From their organs to their skeletons to their fins, a shark’s biology is especially adept at helping them keep afloat in the ocean and thus, helps them to survive.

This buoyancy is even maintained when sharks enter a state of tonic immobility and thanatosis.

This ‘state’ is a way sharks appear dead to predators and will allow them to stay still for up to 15 minutes – but without sinking!

As a result, buoyancy is key to a shark’s survival and thus, it has adapted many aspects of its biology to help it survive.

Mikayla Adams

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