In New Jersey, more than a dozen swimmers had to be rescued from the rough waters.
Along the Jersey Shore, at one point, swimmers were allowed to go into the water waist-deep but that guidance was eventually lowered as tides strengthened.
Some beaches apparently saw waves as high as six feet.
"People are swimming where we aren't, so it's going to take longer for us to respond, longer for us to even notice that you're in trouble, so always just swim in front of a lifeguard," Frank Christy with Ocean City Beach Patrol said. "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."
Ernesto has regained strength and was again upgraded to hurricane status.
Rip tide risk remains in effect on New Jersey beaches until Tuesday.
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