A 16-year-old girl killed in a shark attack was swimming in a river, not the ocean. Bull sharks — considered by some experts the most dangerous — are the rare species that swims in fresh water.

• A teen in Perth was killed by a shark after jumping in a river to swim with dolphins, officials said.
• Officials believe it was a bull shark, a species known for its aggressiveness and ability to swim in freshwater.

Though shark attacks are rare, they most commonly happen in the ocean, off the coast of beach destinations like Florida. But when a 16-year-old girl in Australia was killed in a shark attack on Saturday, she wasn't swimming in the ocean.

Stella Berry was with friends riding jet skis in the Swan River, located in the city of Perth in Western Australia, when her friends said she decided to jump in the water to swim with dolphins that had been seen nearby. Her friends witnessed the attack, with Australian authorities calling it an "extremely traumatic" incident for everyone involved.

Don Punch, the Australian fisheries minister, said on Sunday it was too early to confirm the species of the shark involved, but said that it was believed to be a bull shark.

"We do know that bull sharks, particularly, do enter estuaries and freshwater river systems, so it is likely that may be the case," Punch told the Australian outlet ABC News.

Bull sharks are considered by many experts to be the most dangerous sharks in the world. They are found in waters around the globe and prefer to hunt in shallow, coastal areas — where people also tend to swim — during the day and night. Bull sharks can grow to be anywhere from 7 to 11 feet in length or more, weighing between 200 and 500 pounds, and are known for their aggressive nature — which is also where their name comes from.

Unlike most species of sharks, bull sharks can also swim in freshwater for extended periods of time, hence the reason they are known to enter and swim up estuaries. A study published in 2021 found two bull sharks even swam up the Mississippi River as far north as Illinois on separate trips in 1937 and 1995.

The study said the "rare appearance" of bull sharks in rivers has been reported on five continents. The authors said the "physiological adaptations" that allow the sharks to swim in freshwater, in addition to fossil records, indicate bull sharks have long entered freshwater ecosystems.

Still, although you are more likely to encounter a bull shark in a river than another species, attacks remain uncommon.

Punch told ABC the last deadly bull shark attack in Perth's Swan River occurred 100 years ago, in 1923.

"There's only been six recorded historical attacks in the river, and this would make it seven," he added.

The recent deadly attack has sparked some calls for additional research into bull sharks in the river, with Johan Gustafson, a marine ecologist with Griffith University, telling Perth radio station 6PR that tagging the fish would help researchers better understand them.

"Believe it or not we still don't know a large amount about them — we know broad movements and broad scale behaviors of bull sharks but not the fine details — I think it's a wonderful idea," Gustafson told the station.

In 2022, there were 57 unprovoked shark attacks on humans worldwide, according to the Florida Museum of Natural History's International Shark Attack File. The US leads the world in shark attacks, with 41 recorded last year, while Australia came in second with 9.

Bull sharks, great white sharks, and tiger sharks are the most common species to be involved in an attack.

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