In Ocean City, beaches were closed on Sunday due to thunder and lightning.
According to the Ocean City Beach Patrol, there were major swells in the water due to Ernesto, which upgraded back to a Category 1 storm on Sunday night.
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Beach Patrol Lt. Frank Christy told Action News that Sunday started beautiful and sunny, with many people on the beach until storms rolled through.
Christy said waves reached three to four feet high, and swimmers were able to go in waist-deep, but it dropped throughout the day as the tide got stronger.
He added that there were at least five major rescues in the water due to the intense waves and swimmers who were out of sight.
Christy warned that these conditions, along with rip currents, are dangerous and potentially deadly.
"People are swimming where we aren't, so it's going to take longer for us to respond, longer for us to even notice you're in trouble. So always swim in front of a lifeguard," he explained. "If you're ever stuck in a rip current, make sure not to panic. Try to find help if needed and swim parallel once you feel that rip current subside."
In Ventnor City, beach patrol leaders said waves were rough there as well, with most reaching five to six feet high.
Lifeguards there made 17 rescues on Sunday, authorities said.
A rip current warning is in effect at the Jersey Shore until Tuesday.