Life on the boat is not easy. The crew has no fixed timetable.

"One day in January, we worked from 6 am to 2 am the following morning," said Fang. "But that's normal. Whenever the call comes, we must move quickly."

Because of their busy schedule, none of the seven crew went home for the Spring Festival, the most important occasion in China for family reunion.

"We ate jiaozi (Chinese dumplings), lighted firecrackers and pasted on Spring Festival couplets, like all families do," said the tug's chief engineer, Sun Yisheng.

In Sun's eyes, Fang is a born captain.

"On a boat, everyone has his own job. The captain must keep the team united. Cooperation is essential for ensuring safety. Our captain does a good job of that," Sun said.

According to Fang, there are few options for entertainment on the boat - watching TV, playing cards or just chatting.

"Things are much better today," he said. "We used to have no television on the boat. All we had were a compass, a chart and a radio transceiver."

At that time, before the tugboat sailed, someone had to plot the course on the chart first, he said. If they had to change direction, they had to calculate time and distance based on the speed of the boat before they could turn.

"Now the boat is equipped with an electronic chart system providing instant navigation," he said.

But there are situations that modern technology cannot handle. Fang remembered one boat that was trapped en route to Juehua Island in 2009.

The island, about 27 km southwest from Liutiaogou Harbor, was totally cut off from the mainland by the ice, so local government officials had to send food and medicine to the island by Fang's tugboat.

They hit very thick ice at one point and could not move forward or backward.

"Some large chunks of ice stuck together and became as thick as 40 or 50 cm, wrapping itself around the boat," he recalled. "Our boat weighs more than 300 tons. But it's difficult to crush those big pieces."

They filled the boat's ballast tank with seawater to add more weight, but that did not work directly. Instead, they had to keep adding and discharging water until, an hour later, they managed to maneuver the boat free.

"Frankly, severe weather often makes me feel like quitting the job," Fang confessed. "But I don't know what else I can do as I've been doing this for so many years.

"Besides, I can earn more than 4,000 yuan ($635) per month. That's good pay. My health permitting, I will keep working on the tugboat. I think this is my job for life."