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.
• Bull sharks have been documented swimming up the Mississippi River as far as Illinois.

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.