The body of a 33-year-old man found in Lake Michigan on Thursday is believed to be that of a boater reported missing four days earlier, police said. Emergency crews and police Marine Unit officers found the body at Rainbow Beach near 77th Street. The U.S. Coast Guard and police began the search last Sunday off 55th Street. The man, identified as 33-year-old Omar Salgado, had drowned, according to the Cook County medical examiner's office. Police said the man was boating with three friends when they jumped into the water for a swim. Only three returned to the boat, police said.