Crossing Cook Strait with dolphins and a shark

He was told he wouldn’t have to worry about sharks when swimming Cook Strait.

Then Adam Walker looked down.

A two-metre beast, possibly a great white, was swimming beneath him.

It could have been why he had just been joined by a pod of dolphins, which have been known to protect people from sharks.

Or it could could have been that, in some strange dolphin way, they knew Walker was six swims into swimming the world’s toughest seven-ocean swims, all raising money for the Whale and Dolphin Conservation Society.

"It would be a nice thought they were thinking, we will just help our pal get through."

Either way, it was a magical experience with one getting so close he brushed its tail.

The shark never attacked.

The pod of about 10 dolphins spent an hour on Tuesday swimming alongside him, taking a break to do some acrobatics, during his 8 hour, 36 minute crossing of the strait.

He completed the swim. While it has been done before, nobody previously had done it this late in April when water and air temperatures were low, he said.

Even putting sharks aside – there could have been more than one, he said – the swim was not without its problems.

Not far off setting off from Ohau Bay, west of Makara, he got motion sickness.

"It was like swimming in a washing machine."

He tried to vomit as he swam "but it didn’t work very well" so had to tread water to be sick.

For the majority of the swim he was unable to keep food or liquids down.

Getting close to the South Island he was heading straight for one of the Brothers, islands at the top of the Marlborough Sounds.

With legendary New Zealand swimmer Philip Rush and girlfriend Gemma Clarke shouting encouragement he had to swim against the current to avoid the island.

"I just skimmed past."

Rush, who has crossed Cook Strait eight times, had assured Walker that he would not have to worry about sharks on the crossing.

"I had a go at him when I got out.’’

To complete the seven swims, Walker now just needs to swim the strait from Ireland to Scotland, reputedly the hardest, and certainly the coldest, of the lot.

He has already completed, from easiest top hardest, the Catalina Channel off Los Angeles, the English Channel, the Strait of Gibraltar (it would have been the easiest but he did a return swim), Molokai to Oahu in Hawaii (where he completed the swim despite being stung by a Portuguese man o’ war), Tsugaru Strait in Japan, then Cook Strait – the sixth hardest.

- To see the route Adam swam click here.