Dutch adventurer Ralph Tuijn has reached the halfway point of his attempt to be the first person to row across the Pacific Ocean unaided.

The 16,000 kilometre journey from the coast of Peru to the seaside city of Brisbane, Australia - the widest section of the Pacific - has never been crossed absolutely unaided by a rower, and Tuijn says just nine people have rowed it even with assistance.

Tuijn reached the central point of his crossing - an insignificant point of water in the ocean - 111 days after setting off from Peru in March. He has been making good progress, and has since cut his estimated time of arrival in Brisbane by a month.

The Dutchman, who now expects to reach his destination on October 20, has kept in touch with those tracking his movements through daily internet postings from his laptop, including his wife Winnie. His boat, the Zeeman Challenger, is a seven-metre custom plywood vessel.

Tuijn has overcome a variety of obstacles to reach the halfway point. He is suffering from the constant attention of sharks, who often bump his boat and disrupt his attempts at sleep. One particular shark, dubbed 'Gomulka' by Tuijn, has been trailing the adventurer's boat for extended periods.

He has also accidentally burnt himself when he spilled hot water on his foot whilst trying to make coffee, apparently also from a shark 'bump'. He is also forced to manually pump water for cooking and drinking after his automatic water pump broke down not long into his journey.

Tujin, who is raising money for a children's home in Mumbai, India, is rowing at an average speed of 58 kilometres each day. His diet consists of freeze-dried foods and fish, which are keeping him physically well-conditioned despite tiring mentally.

His vessel has no motors or sails, but relies on his physical rowing power to move. The boat does have a solar power system to provide energy for his laptop, a telephone and a global positioning system.

Tuijn is a serial adventurer and experienced rower. He has rowed across the Atlantic Ocean and the North Sea, as well as cycled across Russia and the icy terrain of Greenland.