Ian Johnston knows the Shank well, but it still finds ways to surprise him.

You won't find this group of rocks on a map, but the veteran mariner is charting their hidden pockets for the benefit of other adventurers.

Mr Johnston regularly sails his converted cray boat along Tasmania's wild south-west coast and has spent his life on the water across the globe.

"I've always had a strong sense of adventure," he told Jane Longhurst on ABC Radio Hobart.

"I love the wild parts of Tasmania."

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The Shank is located along the coast between Strahan and Port Davey and guards the entrance to pristine and secluded coves that can't otherwise be reached.

Mr Johnston said sailors overlooked the area because it wasn't a known anchorage, but he believed it was the best coastline in Australia.

"Tasmania is blessed with having some of the most wonderful, pristine wilderness areas on Earth," he said.

"It's very hard to get there, and if you're trying to get there in a cruising boat, you've got to be very, very careful.

"Everyone goes off their tree with the joy of it."

Megan Stredwick answered Ian Johnston's call for crew members. ( Supplied: Ian Johnston )

His boat Juliene is always ready to go, waiting for the right weather to reach the Shank.

Mr Johnston, a founder of the Australian Wooden Boat Festival, then puts out a call for crew members and off he goes.

Sailing the area is not without its challenges.

"It's multiple rows of rocks, and looking to the west the nearest land is South America," Mr Johnston said.

"When it's rough, it's titanic seas."

Juliene is a converted cray boat. ( Supplied: Ian Johnston )

Mr Johnston said he wanted to map a safe passage and update a rutter (mariner's handbook) he'd written for the Shank.

A high-pressure system brought good weather last week and he and his crew navigated the waters safely.

Once inside, there's rocks that offer protection from severe weather.

"You can come into the outer Shank and get in behind these rocks and drop anchor," he said.

"You're just sitting there with foam streaming past you continuously.

"If you're slightly more sane you can go into the inner Shank."

Ian Johnston uses a drone to explore the area. ( Supplied: Ian Johnston )

Whales up close

Once anchored, Mr Johnston and his intrepid crew spent time exploring the coastline.

"It takes your breath away — at night time, you've never seen such a wash of stars."

There is all manner of bird and sea life, Tasmanian devil footprints on the beach and crayfish aplenty.

A new experience for Mr Johnston was the sight of five humpback whales feeding outside the Shank.

"They came right over and spent 20 minutes swimming right around us," he said.

"They just came over to say g'day."

The crew encountered a pod of humpback whales during a recent journey to the Shank. ( Supplied: Ian Johnston )

Lighthouse delivery

On the return trip, and with spare crayfish on board, Mr Johnston radioed the lighthouse keepers voluntarily marooned on Maatsuyker Island to offer a surprise delivery.

He couldn't reach them but got a call back when the crew was already two hours past the island.

"I had to say, 'We had some crayfish to drop off but you weren't there ... we'll eat them ourselves'."

Mr Johnston said he was hoping to get back to the Shank over the next few weeks and again would wait for good weather and a crew.

"Does anyone want to go with a mad man?"