Police say hopes are fading of finding alive a teenage African migrant who is missing at sea off Perth's Mindarie Marina.

Jenon Biwot, 13, was swimming with a friend at Claytons Beach, 200 metres south of the marina, yesterday afternoon when he got caught in a rip.

He was with another 13-year-old in chest-deep water when they got into difficulties.

His friend was pulled to safety by a man at the beach but a search that lasted until late last night failed to find Jenon.

Another search involving jet skies, boats, aircraft and police divers resumed at first light this morning.

Sergeant Peter Trevitt says every effort is being made to find the boy.

"We're still hoping that we can find him," he said.

"We do have police with the SES volunteers doing a land-based search covering the rock wall and down along the beach, just in case.

"And we'll continue to really smash that area with resources until we get a result."

His father, Materno Biwot, said his family had a long night waiting for news of their son, one of six children.

"When we got the news we were really devastated," he said.

"My family was shattered because of this news and the night was not very short for us; the night had been too long."

Mr Biwot says he is from South Sudan, where he was a schoolteacher, but he was persecuted and fled to Uganda where Jenon was born in a refugee camp.

He spent 18 years in the camp before the family came to Perth three years ago.

"He doesn't swim a lot and he was born in a place where there was no water at all," he said.

Mr Biwot says he would not have allowed Jenon to swim at that beach if he had known he was going.

"He told the mum he was coming to swim, but if I'd learned that I would have stopped him," he said.

"This place is unpatrolled, I wanted him to go somewhere where some people keeping an eye on, specially like the patrol team."

Mr Biwot told the ABC he has little hope his son will be found alive.

"The news is not going well with us, it's quite heartbreaking," he said.

"But, we are very grateful for the support and all the work that is being done here, especially from the police and the emergency services.

"The police have been talking to me quite a lot, they've been very supportive, and even other people that I've met here on the beach have been helpful."

"I'm grateful for the support they've been giving us."

Sergeant Trevitt says a 47-year-old British tourist died when he got caught in a rip in the same area in January.

"This young chap doesn't have a good knowledge of the surf and I believe it was similar with the tourist early on in the year," he said.

"It's quite different conditions when there is a rip; if you're not across what to do when you're stuck in a rip, then it can be quite frightening I think."

Surf Lifesaving WA says rips are more dangerous than the threat of shark attacks.

Its spokesman Chris Peck says 90 people a year drown nationwide after being caught in a rip compared to two deaths a year on average due to shark attacks.

He says it is impossible to patrol every beach along the coast due to a lack of resources and volunteers.