ABC News' Ginger Zee reports:

Rip currents are one of the ocean's deadliest threats and have taken over the Florida coast this summer, causing dozens of rescues and at least one death along the state's beaches this weekend.

In Fort Lauderdale on Sunday lifeguards conducted 23 rescues and assisted many more swimmers from swimming into danger. That same day, a 14-year-old boy identified by police as Dushay Nelson was found dead on Anna Maria Island along Florida's Gulf Coast. The teen went missing while playing in a rip current.

JoAnn Manali waited with Nelson's family as rescuers were looking for his body.

"They told me the boys were out there swimming, they got a little further than they wanted to see them out there," she said.

A rip current rescue was caught on camera a week ago near Wilmington, N.C. Lifeguards there say they have saved at least 50 swimmers from the currents already this year.

Rip currents form as water piles up close to the shore. Then, there is a break in a sand bar along the ocean floor and a fast moving river rushes back out to sea. Within seconds, the current can whisk a swimmer hundreds of yards away from the shore. Rip currents usually form in oceans but also take lives almost every year in the Great Lakes.

The United States Lifesaving Association estimates that the annual number of deaths due to rip currents on our nation's beaches exceeds 100. Rip currents account for over 80 percent of rescues performed by lifeguards, according to the USLA.

The USLA advises to not fight the current if you are caught in one. Instead, relax and swim parallel to the shore and find a break in the current before swimming back toward the shore.

Churning, choppy water is one of the easiest clues to identify rip currents, according to USLA.