Alert JFK Library visitor with a pair of binoculars helps save two men clinging to a buoy in Dorchester Bay

The Boston Police Department reports a kayak trip into Dorchester Bay went awry for two men Saturday afternoon after their kayak took on water and sank, forcing them - and their dog - to swim through 40-degree waters to a nearby buoy, which they grabbed onto, hoping for rescue.

The people suffered severe hypothermia but survived, police say. The dog, however, died.

Police say that somebody on a tour of the JFK Library on Columbia Point turned his binoculars towards the bay, spotted the two at the top of the buoy and called the Coast Guard. A BPD harbor-unit boat then rushed to the buoy, getting there around 6:15 p.m., after the trio had spent about an hour on the navigational marker.

The men were taken to a local hospital for treatment, police say. The dog's body was taken to Angell Animal Medical Center.

Police say they two men had launched their kayak from Carson Beach and made it out into Dorchester Bay when strong winds and choppy seas "became overwhelming" and they tried to turn back, only to have their kayak capsize.