Sharks: A swimmer’s guide

OSS contributor and ecologist Peter Hancock talks to shark expert Dr David Shiffman

Photo by Lubo Minar on Unsplash

Sharks loom large in the imagination of swimmers in the southern hemisphere – and are a terrifying reality for endurance swimmers who have encountered them. Yet of the 440 known species of shark, a third are endangered, and sharks are essential to maintaining the ecosystem that swimmers enjoy. Freshwater ecologist and OSS contributor Peter Hancock, who lives in New South Wales, Australia, talks to conservation marine biologist Dr David Shiffman of Arizona State University about common misunderstandings swimmers might have about sharks – and why dressing up as a sea snake isn’t a good idea.

As a life-long shark enthusiast, one of my favourite things to do is take my 10 year-old son snorkelling with sharks. Sharks have a ‘cool’ factor that extends through generations, and swimming with them is always exciting. Spotted Wobbegong are a type of carpet shark that lie camouflaged in shallow water amongst weed and rock, and we see them frequently along the New South Wales coast. Females keep their eggs inside them for about a year after fertilisation, and give birth to live to about 30 young, each 20 cm long, in September-October. 

Most sharks are the exact opposite of the man-eating killers they’re portrayed as in popular culture and the media. Instead, they’re timid, elusive, creatures that will swim away from us before we even know they’re around, and most don’t even possess teeth capable of fatally wounding a human, let alone sufficient intent to use them. 

With more than a third of the 440 known species listed as threatened, and some of these facing imminent extinction, sharks really need our help. Why Sharks Matter- A Deep Dive into the World’s Most Misunderstood Predator, by marine conservation biologist Dr David Shiffman, provides a fascinating insight into the importance of sharks to us and to the ecosystems we care about. It also provides information on what we can do to help project sharks and their environment. 

As swimmers, we require clean water and healthy marine ecosystems, and sharks are essential for this. They sit at the top of the ocean food web, and control populations of the species below them. Sharks prey on fish, molluscs, turtles, sea snakes, and other ocean animals including plankton. Without sharks, prey populations would increase, upsetting the natural balance and leading to a decline in ecosystem health. A simplified scenario given in the book speculates that removing sharks from coral reefs could result in the reef dying. Coral needs sunlight to survive, and one threat to coral is that of being smothered by algae. Parrotfish graze on algae, keeping the coral clean. Parrotfish are food for larger fish such as groper, and these are eaten by sharks. Without sharks, groper numbers would increase, causing a decline in parrotfish, then an increase in algae resulting in a smothering of coral. We probably could swim in an ocean without coral, but it would be a far poorer experience!    

As swimmers, we require clean water and healthy marine ecosystems, and sharks are essential for this. Without sharks, prey populations would increase, upsetting the natural balance and leading to a decline in ecosystem health.

David Shiffman

Sharks are important to us as swimmers, and as humans, in many ways other than maintaining order in the ocean food web. These are outlined further in David’s easily understood, and well-considered text, and I recently had the chance to ask him a few quick questions about sharks from a swimmer’s perspective.

Q: Many of the swimmers I know also love and respect sharks, but they’re also aware that sharks can be around and that sharks do occasionally bite people. Do you have any advice on helping swimmers avoid sharks? 

A: If you’ve ever been in the ocean, there was probably a shark not that far from you, it knew you were there even if you didn’t know it was there, and it left you alone. Generally speaking, the advice that we give to folks to reduce the already really small risk of a shark bite is to stay close to shore, near other people, and not swim during dusk or dawn. Shark behaviour varies between species, but if you ever see a wild animal behaving in a way that makes you uncomfortable, getting out of the water isn’t a bad idea.  

Q: Why do sharks sometimes bite people? Is it because they’re curious, and biting is one of the ways they test things out? Or do they mistake us for more regular prey species?

A: We don’t know why sharks bite people, but it happens very very rarely. More people die in a typical year from flowerpots falling on their head when they walk down the street. More people are bitten by other people in the New York City subway in a typical year than are bitten by sharks in the whole world. But a leading theory is mistaken identity, they think we’re food because most things in their environment are food. When they taste us and realise we’re not, they let go. 

Q: There are a lot of ‘shark deterrents’ on the market for surfers, divers, and swimmers. These range from eye stickers, wetsuit designs, electric anklets. Do you have an opinion on which ones work?

A: The most charitable thing I can say about commercial shark deterrents is that some of them work sometimes under certain very specific conditions. I think my favourite is a black and white striped wetsuit that makes you look like a sea snake. Apparently no one bothered to check if sharks eat sea snakes, and they very much do. 

Q: What can swimmers do to help raise awareness of shark conservation? Is shark swimming tourism (e.g. with whale sharks in Australia, or basking sharks in Scotland or Ireland) useful in raising awareness of sharks, or does it interfere with their ecology? How does this compare to commercial cage diving with great white sharks?

A: The single most important thing that an individual can do to help save the ocean, including but not limited to sharks, is to not eat unsustainable seafood. Some fishing practices are incredibly harmful to ocean life and environments, while others are sustainable and allow us to still eat healthy, delicious seafood. Wildlife tourism can help, but some wildlife tourism is irresponsible and unsafe. 

Q: We see videos on social media of freedivers pushing down on an approaching sharks nose to guide it away from them. Does this work?

A: Those are notably not random encounters with sharks, those are people who seek out sharks to swim with, often chumming or baiting the water. It’s not a behaviour you need to learn to stay safe because this situation will almost certainly never happen to you.

Why Sharks Matter- A Deep Dive into the World’s Most Misunderstood Predator is published by John Hopkins University Press, and is a great read for any swimmers keen for a balanced and informed overview of sharks, their critical role in the marine ecosystems, and what we can do to help them out.  



Peter Hancock