Two children have been reunited with their parents who went missing while jet skiing at night off the West Australian coast.
The mother and father of the children, aged 11 and five years, set off at 8pm on Wednesday from Port Kennedy, south of Fremantle.
At 11pm, a member of the public found the children alone at a boat ramp, police said on Thursday.
"The plan was for the jetski to be used for a couple of minutes," Senior Sergeant Grant Rosman told reporters.
"Unfortunately the jetski broke down ... It may have not have been intended to leave them for that length of time (but) unfortunately things go wrong."
An air and sea search was launched and 40 minutes later a police helicopter found the woman, 41, and the man, 37, floating on the jet ski about five kilometres off the coast.
"It was very fortunate for the children and the couple, however, three or four hours out to sea is still a long time to be out there," Snr Sgt Rosman said.
"They were in reasonably good health, a little bit dehydrated. We provided them with some water. They were chatty."
A rescue boat towed the jet ski to shore, where the children were reunited with their parents.
"They seemed in good spirits ... I believe they're all doing well," Snr Sgt Rosman said.
The couple were wearing "inappropriate" life jackets and the vessel did not have legally required safety equipment such as flares, navigation lights and an emergency beacon, Snr Sgt Rosman said.
They were also within mobile tower range but had failed to take a phone with them.
"It's extremely frustrating for volunteers and the WA Police Force," he said.
"Take the required safety equipment ... It takes seconds for things to go wrong and those moments can cause people to die out on the water."