The family of a man who has not been seen since going for a swim at a Perth beach earlier this month are holding out hope that he is alive.

Martyn Tann's mother Maree and father Colin made an emotional appeal for anyone with information about their son's whereabouts to come forward.

The 24-year-old was on holiday in Perth, staying with his uncle in Mullaloo and was last seen entering the water about 1pm on April 2.

"We are hopeful that ongoing investigations will bring Martin home to us," Mr Tann said.

"He's a very strong swimmer, at home in the ocean, it is therefore difficult to accept that he is got to grief in the water."

The couple are at a loss to explain their son's disappearance.

"Anything's possible," Mr Tann said.

"It's a big mystery, where the hell is he."

Mr Tann said the searchers, who completed an extensive land, air and sea search across a number of days would have found his son if he had come to grief in the water.

He said police and searchers had left no stone unturned and thanked them for efforts.

"People have been suggesting that maybe a shark [had taken him], there's nothing to support that and dolphins were seen around the area he was swimming, and we'd suggest a large predator would scare the dolphins away," he said.

The couple said they had no idea where their son could be.

"How can a person just disappear?"

Mr Tann said his son was not the type of person to vanish for periods of time without contacting family.

He said the family were coping the best they could.

"We have our ups and downs; we're clinging on with hope," he said.

Mr Tann said Martyn's uncle Trevor, who he had been staying with, had been at the beach searching every day since his nephew went missing.

"It's been very tough, particularly for Trevor," he said.

"Any piece of information could be vital in solving Martin's disappearance."

He asked anyone who has any information on his son's whereabouts to call Crime Stopper on 1800 333 000.

Martyn, who is originally from New South Wales had come to Perth after eight months of travelling and planned to head to Broome to work, earn money and then start another adventure in Europe.