In the middle of the glistening sheet of frozen sea, Captain Fang Yusen, 59, was at the wheel of his tugboat Jinshuiqiao 6 clearing a passage through the ice to Liutiaogou Harbor at Huludao, in Northeast China's Liaoning province.

"Even when there's no need to guide ships to and from port, we have to go out every day. Otherwise, vessels might become icebound at sea," Fang told me when I boarded his boat.

Now it was snaking its way through the ice field to rescue a trapped navigation buoy.

Crashing noises continuously came from the tug's hull until it hit thick ice and could not move forward. Fang reversed his boat and then accelerated full ahead. After three tries, he made it and reached the buoy.

Three crewmen got a rope around it and pulled it in.

"The sea ice is powerful. It kidnapped the buoy, which was fixed to a cement block, and took it 9.2 km away," Fang said.

The Bohai Sea freezes every year. Floating chunks of sea ice can extend up to 100 nautical miles (185 km) from the coast. The Liaodong Bay, where Huludao is situated, is one of the most affected areas.

Fang said there are three tugboats at Liutiaogou Harbor. These days, all of them are as busy as bees from morning to night, breaking ice, carrying food supplies to ships at anchorage, and performing their designated task of towing big ships in and out of the harbor.

A native of Shenyang, Liaoning's provincial capital, Fang has been working on tugboats all his life. The veteran used to be a signalman on one in Dalian, Liaoning, when he served in the army. He started working on a tugboat at Huludao after leaving the army.

"My father took me to Huludao in the late 1950s. It was the first time I saw the sea and wished I could live by the seaside. But I didn't expect that I'd be living on it for nearly 40 years," Fang recalled.