EVANSTON, Ill. (WLS) — Lighthouse Beach is off-limits while crews continue their search Monday for a swimmer who disappeared after jumping in the water.

The Evanston Fire Department was back on Lake Michigan on Monday morning, resuming their search for the man who went missing in the water on Sunday afternoon.

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Assisted by Chicago and other suburban fire departments and the U.S. Coast Guard, crews, for now, are focusing on a half-mile area starting at Lighthouse Beach and heading south. They are using sonar and other technology, but the turbulent water is making things difficult.

“Even our rescuers this morning, during the search effort, was reporting extremely hazardous current and wave conditions that they were facing as they were in their vessels,” said Matt Smith with the Evanston Fire Department.

It was Sunday afternoon when an emergency call came in regarding four swimmers struggling in the water.

Joe Flanagan said he saw everything unfold.

Flanagan was at Lighthouse Beach with his son-in-law and grandson. He said two teenage girls were having difficulty in the water when a woman and a man jumped in to help them.

“It just didn’t look like everything was going well, so I got down to my shorts and jumped in water, grabbed mother and the daughter, and one of the other girls, and pulled them up,” Flanagan said.

Flanagan got the teen girls and the woman to safety, but when he went back in to look for the man, he could not find him. He said a red flag was up at the beach, signifying no swimming. He says it is important for people to heed safety warnings.

“The only reason I’m here right now, talking to you, is because people have to know that this is really dangerous. That water is incredibly dangerous,” Flanagan said.

Just Monday morning, a man died after being pulled from the lake near Montrose Beach.

Dave Benjamin with the Great Lake Surf Rescue Project said around 50 people drown in Lake Michigan each year, and that knowing how to swim does not guarantee survival.

“Essentially, what we need people to do is float to live, float to survive. They need to flip over on their back and float, stay on the surface until they can either self-rescue, or a professional can rescue them,” Benjamin said.