SANDY HOOK - The air and marine search for a swimmer who went missing in the waters off Sandy Hook has been called off for the day.

Park rangers will be searching along the beaches periodically and a Monmouth County helicopter will fly over the area occasionally. The search is expected to resume Friday.

The 25-year-old man was swimming with friends and family at around 7:30 p.m. Wednesday when he disappeared in the water. There was no lifeguard on duty at the time.

A search effort began soon after, but was called off after several hours.

The search resumed Thursday morning. Divers and marine units from Monmouth County used side-scan sonar to search the water, but were not able to locate the missing man.

Gateway Recreation Area spokesperson Daphne Yun warns swimmers against swimming in areas without a lifeguard.

"We want all our visitors to stay safe, that's a message that we really want people to take home. Swim at lifeguarded areas," she says. "If you can't swim, don't go in the water."

The identity of the missing swimmer has not been released.