Around the world walker set to swim Caspian Sea

Karl Bushby plans to swim across the Caspian Sea to Azerbaijan, continuing his round-the-world challenge

A Hull man hoping to become the first person to complete an unbroken walk around the world is planning a 186-mile (300km) swim across the Caspian Sea.

Karl Bushby set off in 1998 and is more than two-thirds into his 36,000-mile (58,000km) adventure.

However, he said tensions between the West and Russia and Iran have meant the only option open to him if he wants to continue is to swim from Kazakhstan to Azerbaijan.

The ex-paratrooper said: "This is the best route, because it's the only viable route. Failure here would be crippling."

Karl Bushby set off from Hull in 1998 and has been on the road ever since

Under the rules he set himself before beginning his adventure, which he has called the Goliath Expedition, Mr Bushby must not use any form of transport.

According to his research, no-one has ever swam across the Caspian Sea - the biggest enclosed, inland body of water in the world.

He said he intends to set off on the swim in mid August.

Backed up by a support boat, he will be joined in the water by two members of Azerbaijan's national swimming team.

Mr Bushby said: "We have to be aware something very simple could doom this. A torn rotary cuff, pulled muscles, something along those lines could be real bad."

Mr Bushby has completed roughly two-thirds of the journey

Explaining his decision to take to the water, Mr Bushby said: "Being unable to cross Russia or Iran, north or south of the Caspian, means the shortest possible route - across the Caspian Sea - is next best."

Mr Bushby admitted he had "limited swimming experience", although he cited "a few days floating down the Atrato River" in the jungles of Colombia, as well as crossing the Bering Strait and navigating the Aldan River in Russia.

"I’m definitely not a swimmer, nor do I like swimming," he added.

In training Mr Bushby has been completing regular swims of up to 10 miles (16km), as well as gym sessions.

The swim will be "more strategy than brute force", he said, adding "the idea is to be in good shape by the end of each day, not a physical wreck".

He said he aims to complete a minimum of 6 miles (10km) per day, expending as little energy as possible.

Mr Bushby said the Azerbaijani government is helping fund this stage of the expedition.

He said: "They [Azerbaijani government] have pretty much saved the day, stepping in just as it became clear we would not reach our funding goals this summer."

'Unexpectedly harder'

Mr Bushby described the progress of the expedition so far as "so far, so good".

Conceding progress had, at times, been slow, he added: "Slow progress is still progress in a troubled world. I've been lucky so many times.

"I will say in the latter half, it's being tougher, without doubt due to isolation. In general, not having a close relationship with anyone.

"Being alone is becoming suddenly and unexpectedly harder. It’s something I didn’t necessarily think would have been a problem or had the impact it is having."

Mr Bushby said he was unable to say when he will cross the finish line in Hull.

"There is a lot to unfold between now and then," he said.