CHICAGO (CBS)–A yacht carrying 49 passengers Saturday night on Lake Michigan was guided back to shore by the Coast Guard after getting lost in dense fog.

The 56-foot yacht was drifting near Navy Pier around 11 p.m. near a breakwall when a passenger called 911 with concerns the boat operator had become disoriented in heavy fog. Coast Guard officials said visibility was less than a quarter-mile.

The yacht, which did not have a working navigation system, was escorted into Monroe Harbor by a rescue boat from the Chicago Maritime Safety Station near Navy Pier.

Rescuers were guided to the distressed vessel by talking to the passenger on her cell phone. With almost no visibility, she relied on the sound of the approaching rescue boat’s horn and notified rescuers as they neared the boat.

The Coast Guard found the vessel, named “Serenity,” transiting slowly. Ater it was guided back to shore, safety inspectors boarded the boat and found no working radio system or GPS. The boat was also not carrying enough life jackets, according to the Coast Guard.

The boat operator was issued a violation for negligent operations and for operating without the required navigation lights.