Rumson police say that people planning on swimming or boating in the Navesink River this weekend should be sure to keep an eye out for sharks.

The warning comes after reports of several bull shark sightings near Navesink Avenue in town.

Police have not been able to 100% confirm the sightings of the bull shark in the river. But in a post on Facebook, police say, “There have been several reports of possible bull shark sightings in the Navesink River in the area of Navesink Avenue in Rumson. NJ Division of Fish and Wildlife has been notified. They advised that no sightings have been confirmed as of yet but, as always, there is a possibility that sharks could be in our local waterways.”

“The waters are a bit healthier than they have been and the food chain is growing,” says scientist Jessica Staats. “The smaller fish are in more abundance, which means the bigger predators have more to eat."

A bull shark is considered to be dangerous to humans because it can swim upstream in freshwater.

According to Robert Heyer, author of "Shark Attacks of the Jersey Shore," documented attacks in the Navesink and Shrewsbury rivers go back to the late 1800s, especially during hot summers and when prey is abundant. He says they are most likely to feed at dusk and in groups of three.

A series of shark attacks at the Jersey Shore in 1916 was part of the inspiration for the novel “Jaws” and the 1975 blockbuster movie.

Experts say that swimmers who may spot a shark should not make any sudden movements and either get to the shore or swim calmly to a boat.