Rod Moore is planning to walk off the Western Australian coast for about four kilometres, from North Fremantle to Cottesloe Beach, on April 18.

This will be Mr Moore's sixth underwater walk. His first was in 1987 along the eastern fringes of Lake Macquarie, and he repeated that feat 30 years later to raise money for charity.

Since then he has walked under Sydney harbour, off Bondi Beach, and along a section of the Gold Coast.

He is undertaking this latest walk to raise awareness of the Kiwanis International service clubs.

Rod Moore said he was looking forward to the submarine stroll in Western Australia, even if he may be sharing it with sharks.

"It's a state I haven't done, and also there are big fish over there," Mr Moore said.

"But I don't want them biting me."

Initially, to keep big fish - and his own fears - at bay, Mr Moore wore a home-made steel-mesh contraption. These days he wears a commercially made shark shield.

On the surface will be a crew of five in a boat, feeding him air down a line and making sure the 57-year-old is okay.

Leading the support team will be David Smart, from Smart Subsea, a Perth commercial diving operation.

David Smart said he was pleased Mr Moore would be wearing a shark shield.

"There's a real chance he'll see sharks," said Mr Smart. "You generally see reef sharks, but we do get great whites as well."

Rod Moore is not sure for how long he will be underwater, but he expects it will be for up to five hours.

However, "it depends how the foot goes". His right leg can give him trouble. His foot was severed by a boat propeller and was surgically reattached more than 20 years ago.

He will be walking at depths of between four and nine metres. At least the underwater trail should be relatively soft.

"It's a fairly sandy bottom, with the usual bits of reef, so it should be a nice walk for him," said Mr Smart.

One member of the local support crew, Colin "Spud" Murphy, completed a marathon underwater walk of about 20 kilometres from Rottnest Island to the mainland eight years ago.

He's been advising Mr Moore on where to walk, and what to expect.

"I might jump in for a look; follow him along for a bit," said Mr Murphy.

"He shouldn't have any problems.

"The water's so clear, you've got great visibility."

David Smart is an experienced diver, having worked in the offshore oil and gas industry. But this is the first underwater walking mission he has been part of.

When he was approached by Rod Moore with this idea, Mr Smart's reaction was "Really?". But then he jumped on board to help out the Kiwanis International clubs.

However, Mr Smart will be staying on the boat, saying the prospect of walking under the waves "doesn't excite me greatly".

Before he has even conquered the west, Rod Moore is already dreaming of new adventures in even more distant waters. He is looking at the American west coast or the Caribbean.

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