Bangkok (CNN) Workers on an oil rig some 135 miles (220 kilometers) off the coast of Thailand found an unexpected new friend swimming nearby: a dog.

The brown canine was found paddling near the rig, cold and shivering, with no indication of how he got there.

Rig worker Vitisak Payalaw, an offshore planner with Chevron, told CNN that fellow staff members spotted the dog swimming towards the platform on the afternoon of April 12, and held out a pole for him. But, buffeted by the waves, he was unable to climb up, his grasp repeatedly slipping.

"I thought that if we didn't move quickly, I would not be able to help him," said Payalaw. "If he lost his grip, it would be very difficult to help him."

Workers threw a rope around the dog to rescue it from the sea.

Payalaw described how the dog simply held on silently, looking up at the workers.

Read More