'They've just ditched': Dramatic audio released after light-plane crash

Dramatic air traffic control audio has captured the frantic moment a light plane crashed into the ocean off Western Australia.

A 70-year-old pilot and 62-year-old passenger made a lucky escape after a light aircraft plunged into the ocean off popular City Beach in Perth on Saturday.

The incident came after the pilot reported engine troubles during a joy flight and was forced to ditch the small plane.

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The two men were able to get out of the aircraft and swim approximately 20m to shore following the controlled manoeuvre.

Today, dramatic air traffic radio between the control tower and a pilot of a nearby aircraft has been released.

"I can see they're very low, looks like they're heading towards the beach," the pilot of the nearby plane can be heard saying.

"Yep that's what they've just advised, can you just monitor or stay overhead them and just advise if you see any passengers get out," the control tower operator replies.

"Just to let you know they've just ditched into the water. I saw them ditch in the water, about 10m from the beach," the pilot interjects.

Experts say the pilot would've had only 30 seconds between recognising the engine was failing and landing the plane.

"The chances of engine failure in a single engine aircraft with that kind of engine are about 13 per 100,000 flying hours, so it's not that common but it does happen," aviation expert Tim Collins said.