Chinese fishermen in the South China Sea not only face the perils of the open sea, but also the danger of an encounter with a foreign patrol boat. Our reporter Han Bin visits Tanmen town in South China's Hainan province. There he found the rising territorial tensions are having repercussions back on land.

Heading South.

To meet a veteran fisherman and honored captain.

This man has spent his lifetime in the South China Sea.

No one seems to know the area better.

Su Chengfen now lives in Tanmen town, in Hainan province.

The 80-year-old is building a model of the boat he took with his grandfather.

They sailed to the Nansha Islands, also known as the Spratlys, when he was 13.

"This is the head sail, this is the main sail and that's the tail sail. When storms are really strong, we close down the sails, just to make sure the boat will not overturn. The waves toss the boat up and down. Water inundates it. It's so dangerous," Su said.

Su Chengfen showed me the secret of his voyages.

It’s a navigation log of the South China Sea.

Tanmen people call it “Genglubu”, which means the “Road Book”.

There are numerous versions, centuries of hard-won experience.

Every island and its surrounding conditions are clearly described.

Chinese experts believe they are clear evidence that Chinese fishermen were the first explorers in the South China Sea.

"With the increasing complexity of disputes in the South China Sea, many surrounding countries have intensified their actual control over the islands and reefs. Chinese fishermen have been harassed more often in traditional fishing areas. Some have been expelled or detained. It will be a big challenge to maintain normal fishing and exploration activities and protect the islands," said Wu Shicun, president of National Institute for South China Sea Studies.

The people of Tanmen have been fishing in the South China Sea for generations.

Before he retired at 60, Su Chengfen used this compass and the “Genglubu” on all his journeys.

In 1972, he was detained by Vietnam.

Since then, he has never returned to the Nanshas.

"We go fishing in the South China Sea because we regard this area as our home waters, or our Ancestor's Sea. It's also because we hope to defend our territorial waters from encroachment by other countries," Su said.

Tanmen is a very small fishing town, which has become well known, as its residents work on China ’s maritime frontier. Fishing is a long tradition here, but it’s not just about money. Life for the fishermen is extremely hard, and the disputes and unrest are making it harder. They hope that they can carry on in peaceful waters.

A big boat, big fish and sailing on the open waters.

That's what Su Chengfen wants for his grandchildren.

He knows he's too old to return to the sea.

But he hopes the fishermen of Tanmen can continue to cast their nets.