Surprise! Sharks Lurk in These 10 Lakes

If you developed a phobia of swimming in the ocean after viewing Jaws as a child, you probably found some comfort in believing that sharks couldn’t get you in a lake. Wrong!

Although great whites and most shark species cannot survive outside of saltwater, several species — including the aggressive bull shark — are tolerant of brackish water and freshwater as well. This means that the sharks can swim upstream via estuaries and into lakes far from the nearest ocean. Cue the Jaws theme music and keep an eye out for unexpected dorsal fins!

You’re more likely to find a catfish or sturgeon in a lake than a man-eating shark, but that doesn’t mean people haven’t spotted something fishy in various lakes around the world. Here are 10 lakes in which sharks made surprise appearances.

Lake Nicaragua, Nicaragua

Lake Nicaragua is the largest lake in Central America. Once an inland bay, volcanic eruptions transformed it into an inland basin that trapped various oceanic creatures, including bull sharks and sawfish, a close relative of sharks.

Today, bull sharks swim up the San Juan River and into the freshwater Lake Nicaragua, sometimes staying there for years if food remains plentiful. Like salmon returning upstream to spawn, bull sharks are known to jump over a series of eight rapids to enter Lake Nicaragua — a behavior not seen by bull sharks anywhere else in the world.

Lake Pontchartrain, Louisiana, United States

Lake Pontchartrain is an estuary near New Orleans that covers 630 square miles. The 23.83-mile Lake Pontchartrain Causeway that crosses the lake is the longest continuous bridge over water in the world.

A bull shark attacked a seven-year-old boy in Lake Pontchartrain in 2014 — the first recorded attack of its kind in the area. Fishermen have spotted bull sharks up to six feet in length in the lake.

Mostly juveniles, the sharks swim into the lake during the summer months and then return to the Gulf of Mexico in the fall. The lake makes an ideal nursery for the growing juveniles before they graduate to hang with the big fish in that bigger pond known as the ocean.

Carbrook Golf Club, Queensland, Australia

Florida golf courses are known to sometimes have alligators in the surrounding water. At the Carbrook Golf Club in Queensland, Australia, however, more than a dozen bull sharks inhabit the oxbow lake at the edge of the golf course.

It’s believed that the sharks were washed into the lake during a flood event in the 1990s. Now some of the sharks are reported to be as long as 10 feet. So, if you’re golfing at Carbrook Golf Club and knock a ball into the water, just leave it.

Lake Michigan, United States

There are no official reports or scientific data proving that sharks lurk in Lake Michigan, but numerous unofficial sightings have been reported over the years.

In 1969, a couple of fishermen reportedly pulled a dead 29-inch shark onto their boat. Later, locals discovered a dead bull shark washed up on shore and people have reported seeing dorsal fins in the water near Frankfort, Michigan.

We know that bull sharks can survive in freshwater, so it’s not completely out of the realm of possibility that a few may have made their way into the Great Lakes at some point in history. Out of all the lakes on this list, however, this is the one where you are the least likely to encounter a shark.

Lake Maracaibo, Venezuela

Venezuela’s brackish Lake Maracaibo is the largest lake in South America and one of the oldest on Earth, estimated to have formed 36 million years ago.

Sharks are some of the most ancient fish on the planet, so it’s not too outrageous to imagine that they’ve been swimming around in Lake Maracaibo for millennia. Like Lake Pontchartrain in the United States, bull sharks reportedly use Lake Maracaibo as a nursery.

Lake Izabal, Guatemala

Lake Izabal is the largest lake in Guatemala, covering nearly 228 square miles with a maximum depth of 59 feet. The lake drains into the Caribbean Sea’s Gulf of Honduras.

Both bull sharks and sawfish, a type of ray and relative to sharks, have been sighted in Lake Izabal and are usually found living in the same bodies of water together. There are 70-year-old records of two reported bull shark attacks in Lake Izabal.

Lake Sentani, Papua, Indonesia

This tropical, remote lake in the Papua province of Indonesia is home to bull sharks and sawfish.

During World War II, a soldier reportedly dropped a grenade in the lake, hoping the explosion would bring food to the surface for his fellow soldiers. A largetooth sawfish, now a critically endangered species, is one of the fish that floated to the surface for the group.

Bayano Lake, Panama

Bayano Lake is a manmade reservoir created after the Bayano River was dammed up in 1976. It is now the second-largest lake in Panama, following Lake Gatun.

Although both bull sharks and largetooth sawfish were trapped in the lake in 1976, bull sharks are not known to reproduce in fresh water. Since the upper-limit life expectancy of bull sharks is about 30 years, it’s unlikely that any bull sharks still remain in Bayano Lake unless, like they say in Jurassic Park, life found a way.

Sabine Lake, Texas, United States

Sabine Lake is one of several estuaries located along the Gulf Coast of Texas. The lake connects to the Gulf of Mexico via the Sabine Pass.

According to PBS, researchers have found more and more baby bull sharks in estuaries such as Sabine Lake. One theory of why bull sharks use these brackish estuaries like Sabine Lake as nurseries is that the tiny sharks are protected from larger sharks eating them.

A baby bull shark in Sabine Lake won’t get eaten by a great white, tiger shark, or other large fish that can only survive in the ocean.

Lake Merritt, California, United States

Lake Merritt is a brackish tidal lagoon located in Oakland, California that formed about 10,000 years ago. It is notable for being the first official wildlife refuge in the United States.

In 2020, Newsweek reported that a leopard shark was filmed swimming in Lake Merritt. The spotted leopard shark is commonly found in the waters off the California coast, but it’s unusual to find one so far inland. Unlike the bull shark, the leopard shark is mostly harmless to humans when the fish is alive.

Sometimes people eat the meat of the leopard shark, but the California Department of Fish and Wildlife advises against doing so because the fish are full of mercury and other pollutants.