The crew of a fishing vessel rescued a Portland man who fell off the Peaks Island ferry Tuesday evening.

The Coast Guard said in a press release that the 54-year-old man was a passenger on Casco Bay Lines’ Aucocisco III when he fell into Portland Harbor around 5:15 p.m.

The Coast Guard said crewmen working on the fantail of the fishing vessel Christina & Caelyn saw what they initially thought was a harbor seal in the water near South Portland’s Bug Light. They realized it was a man only after he waved at them. The boat’s captain called the Coast Guard, which launched a rescue boat from its South Portland station.

By the time the Coast Guard crew arrived, the fishing boat had pulled the man out of the water – which was 38 degrees. He was in the water for about 20 minutes. The man was taken to the Maine State Pier, where an ambulance crew took him to Maine Medical Center for treatment of hypothermia.

The Coast Guard would not identify the man Tuesday evening because the cause of the mishap remains under investigation. The name of the fishing vessel’s captain was not available.

“This lucky man is alive today due to the quick response by the Christina & Caelyn captain and crew,” said Coast Guard spokesman Lt. Connan Ingham. “Even though the ice is gone the water is still very cold.”

The man was in stable condition Wednesday morning at Maine Medical Center, according to a Coast Guard spokesman.