A man held his phone above his head as he tread water in Lake Michigan until he and another man were rescued Friday after their boat sank in Lake Michigan, the U.S. Coast Guard says.

The two men, 29 and 31, were about a mile east of Waukegan Harbor in Lake County when their 15-foot bass boat started taking on water. The vessel sank within 10 minutes, the Coast Guard said.

Coast Guard Station Kenosh launched a rescue boat after the man with the “partially waterproof” phone called them shortly after noon. The water was 58 degrees, the Coast Guard said.

“The first person rescued did not have a life jacket on and was treading water while holding onto a small, boat fender,” the Coast Guard said in a news release. “The second person had his life jacket on backwards and was holding his cell phone above his head to keep it dry while treading water. Both men were exhausted and cold from being in the water nearly 45 minutes.”

The men told their rescuers they believed a new plug they bought for the boat, possibly falling out, was to blame for the leak.

The men did not have a “float plan” and did not tell anyone they would be out the water, according to the Coast Guard.

“The Coast Guard urges boaters to have a plan when they go out on the water, to carry multiple signaling devices, to have enough working life jackets, and to bring an electronic position indicating radio beacon,” the release said.