When 7-year-old Trent Trentacosta felt something bump into him while swimming in Louisiana's Lake Pontchartrain, he never imagined the shove would turn into a shark bite, but it did, according to USA Today.

Experts believe the boy's attacker, who bit his foot, was a 5-foot long bull shark.

But are there sharks in lakes?

The answer is yes- at least in Lake Pontchartrain, according to Martin O'Connell, University of New Orleans researcher and chair of their Earth and Environmental Sciences Department, who stated that bull sharks like the mix of salt and fresh water the lake offers.

"Bull sharks can adapt their osmoregulatory processes to survive in a broad range of water salinities, from the salt water of the ocean to the fresh water of a lake," according to Shark Savers. 

But you shouldn't worry that much.

O'Connell says 99 percent of the bull sharks in the lake are young "and [use] the lake perhaps as a nursery," he told WGNO ABC. 

Shark attacks are very rare, according to John Carlson, a research biologist at the National Oceanic and Atmospheric Administration's Fisheries Service in Florida.

"I can't recall the last time there was a shark attack in Lake Pontchartrain," he told Live Science.

"You have a better chance of being struck by lightning on a golf course," Carlson added.

But why would a shark bite Trent?

Sharks will commonly mistake the movement of a human foot for a mullet or catfish. But when the shark goes to bite it and realizes it's not food, "We call it 'bite and run,'" Carlson said.

If you're worried about your next lake visit, you should avoid being in visibly low water during dusk or dawn, don't wear shiny jewelry, swim in groups and don't swim near fishermen, Carlson told Live Science. 

Trent Trentacosta is expected to make a full recovery.