Are sharks dangerous?

One of the most frequently asked questions for those new to diving is about sharks… “will there be sharks?”, “are they dangerous?”, “what do we do if we see sharks?”. But if you ask any diver, sharks are one of the best things to encounter on a dive and something we hope to see!

Thanks to Hollywood and films like “Jaws”, people think the sea is filled with terrifying and man-eating sharks that are just waiting for us to jump in so they can attack.  However, the truth is, not only are sharks incredibly important part of the marine ecosystem, they are not the blood thirsty monsters people have been made to think.

Sharks are apex predators (just like humans), this means they are at the top of the food chain. As such they regulate populations and are vital in maintaining a balanced ecosystem.

Does this make you feel scared or peaceful?

Species of Sharks

There are over 500 species of sharks and they come in all shapes and sizes. Yes, there are the "classic" sharks, which is what you may be thinking of, including the Great White Shark, Bull Shark and Whale Sharks, but there are many more species sharks of in all sizes, colours and varieties. The carpet sharks are fascinating, and include the Wobbegong shark and the beautiful Zebra (Leopard) Shark. In the depths of the ocean, you can find strange looking sharks that can live for hundreds of years like the Greenland Shark and then you can get the true giants like the Whale Shark or Basking shark – both eating only plankton! There are also tiny cute little sharks like the Dwarf Lanternshark and Pigmy sharks - only around 25 cm in length

Quick Facts

A smiling Zebra Shark

• Sharks are cartilaginous, meaning their skeleton is made of cartilage, not bone.   

• Sharks have gills to breathe and an oily liver for buoyancy (unlike boney fish which use a swim bladder).

• Sharks have an advanced sensory system, which includes the lateral line and

  electroreceptors called ampullae of Lorenzini  which allow them to sense movement via electromagnetic fields and vibrations in the water.

• Not all sharks have to swim to breathe, in fact many shark species have an organ called a spiracle, which allow them to pump water through their gills when still.

• Different species of sharks have different shaped teeth depending on their diet – and their jaw is like a conveyor belt, continually replacing their teeth throughout their life.

Sharks and Blood

Again, thanks to Hollywood and misinformation, it is widely believed that if you put just 1 drop of human blood in the ocean, you will instantly get a mass of angry, hungry sharks!

It is true that sharks generally have an exceptional sense of smell, and can detect an odour in water in concentrations of up to one part per million. They are also very clever and like to reserve their energy. When they sense a fish in the ocean, they make a calculation to work out if the energy they would gain from eating it, is more than the energy it would take to catch it. Thus, they will generally only catch weak, dying or injured prey (rather than waste a lot of energy chasing a healthy and energetic fish for a relatively little snack). This is part of the reason Sharks are so important, they keep the population healthy!

A Whale Shark feeding

Like you, sharks know what they like to eat. They have been around hundreds of millions of years – way before humans. As such, we are not on their menu. They may be able to smell human blood if it is in the ocean – but they know relatively little about us. They cannot calculate accurately how much energy it would take to catch us and we are simply not on their favorite food list! Imagine someone putting dog food in front of you – you would know that it is “food”, but unless you are really, really desperate, you’re not going to eat it!

Shark Behaviour

A Shark can be understood by its behavior – much the same as you would be able to tell a human was upset, happy or angry by the way they act and react to situations, we can do the same with sharks. It is important if you are going to enter the water with these animals, that you understand how to read them and know when to back off!

Normal characteristics:

Many sharks swim around with their mouth open – in humans this may be a sign of anger, but in sharks, this is simply how they are. They also can open and close their mouth quickly and with force (almost like a shark sneeze) this could look aggressive, however, it is most of the time, simply the shark either clearing their gills or resetting their jaw – another normal shark behavior.

A toothy grin, doesn't mean a monster

Staying in the passive position

Generally, a shark will view anything above them (shallower) as a dominant position. Surfers and swimmers, who remain on the surface, are in a natural dominant position over the shark, which may make the shark feel threatened. As divers, we are able to get below the shark, and remain in a passive position, meaning it wont sense a threat from us. Additionally, swimmers and surfers tend to splash around a lot (unlike divers who are calm and serene), sharks could potentially pick up on these vibrations and think we are an injured, easy meal!

Body language

When a shark is at ease, their pectoral fins will be wide and flat, they will swim calmly and look relaxed. When a shark feels threatened or want to signal dominance they may start to show signs of agnostic behavior which can include:-

-        Depression of the Pectoral fins (pushed back or lowered)

-        Figure of 8 swimming or circling

-        Arching the back and raising of the snout

-        Head shaking

If you see these behaviors in sharks, simply swim away slowly and perhaps deeper in the water.

Conclusion

So sharks are not the monsters they are made out to be. They are a vital part of the marine ecosystem and we pose a much larger threat to them than they do to us. As long as we understand sharks, read their behavior and respect their space, we can continue to enjoy watching these magnificent and diverse creatures when we dive, without them being conceived as dangerous.

We love to see sharks on our dives! Here in Nusa Penida we can see the White Tip Reef Shark, Bamboo shark and Wobbegong shark. Very occasionally our divers have also been lucky enough to spot Whale Sharks, Thresher Sharks and Hammerhead Sharks – what will you see on your next dive?