Sunfish pictured off Pembrokeshire by photographer Janet Baxter

The Grey family were fishing off the coast of Pembrokeshire when the ocean sunfish - weighing around 30kg - landed on top of their son Byron.

"It knocked him flying," said Vivienne Grey, from Little Haven.

Sunfish - the world's largest bony fish - are native to warm, tropical waters and are less common in the UK.

Mrs Grey and her husband Andrew had taken Byron and his brother Owen, 12, fishing for lobster in their 14ft boat. They were about 150m off the coast of Little Haven when the incident happened.

"My husband said he was glad we went with him, because he's sure we wouldn't have believed him if he'd come home and told us about it," she said.

OCEAN SUNFISH FACTFILE Its scientific name is Mola Mola - also known as the moon fish It is flat and disc-shaped in appearance, with a distinctive fin It can grow up to 3m long and weigh 1,360kg It is found in most of the world's tropical and temperate waters - often along the coastal areas where gulls can rid them of parasites Like many other unusual sea creatures, it is becoming more common in Welsh waters It has a small brain - a 200kg specimen may have a brain the size of a nut

"We spotted the fin of the sunfish in the water and, because we knew they were rare, we thought we'd take the boat a bit closer to let the children have a look.

"But as we got closer, it just disappeared. The next thing we knew, it had leaped out of the water and landed in the boat, right on top of Byron.

"We grabbed him from under the fish, and both boys were just shouting to their dad to get the fish out of the boat.

"It was very heavy, but Andrew managed to lift it and heave it over the side.

"Luckily, Byron got away with cuts and grazes.

"I didn't realise there were fish that big in our waters."

The experience has not put the family off sailing, and the boys were back out in the boat within days.

Marine-watchers said several sunfish - which normally live in warm, tropical waters - had been seen off the Pembrokeshire coast in recent months.

'Not dangerous'

Cliff Benson, who runs Sea Trust, the marine branch of the Wildlife Trust of South and West Wales, said sunfish could grow up to 3m long and weigh up to 1,360kg (3,000lb).

"We get them through the summer months, but normally all people see is the distinctive grey fin," he explained.

"They float about eating jellyfish, and our waters are particularly rich in jellyfish at the moment.

"They're not considered dangerous. In fact, only one man has ever been killed by a sunfish - and that was because it landed on him and squashed him."

Wildlife photographer Janet Baxter, from Borth, who took the picture of the fish above, said sea creatures leapt out of the water for all kinds of reasons.

"I saw two young sunfish jumping around last year," she said.

"The usual reasons things jump out of the water are because of food, sex, or parasites - but sometimes they just do it for the fun of it, because it's a nice feeling."