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On a warm summer's day, somewhere near the Cape Verde Islands off the coast of Africa,

Robin Knox Johnston puts on a mask and a snorkel and jumps from the side of his yacht into a calm sea.

It sounds idyllic.

But Knox Johnston isn't diving for fun.

He's investigating why his boat has been leaking.

You expect some water in the bilge, but not this much.

He's been having to run the pumps twice a day.

Five feet below the waterline, he sees the problem. Two wooden planks are coming

slightly apart. A long, thin gap has opened up between them. As the boat bobs gently in

the ocean, the gap opens and closes.

Opens and closes.

It's no big deal.

Every boat needs patching up from time to time.

In an ideal world, Knox Johnston would simply have the boat lifted out of water when he's

next at port and fill the gap with

corking cotton, picture a thick piece of string. But he can't head for a port because Robin

Knox Johnston is competing for the Sunday Times Golden Globe. The year is 1968.

The challenge, sail around the world, single-handed without stopping.

It's never been done before.

Knox Johnston will have to repair the gap right here in the middle of the sea,

underwater on his own. But how? He ties a hammer to a rope and dangles it overboard. He twists a length of cotton, dives under the water, hammers it into the

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