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This is the moment one of the world’s heaviest bony fish greets a gobsmacked family off the coast of Wales.

Sililo Martens couldn’t believe his eyes as he recorded the encounter, as people on his fishing trip discussed whether they could see a shark or a dolphin lurking under the water.

But as it got a bit closer a passenger can be heard saying: ‘No it’s not, look how big that is, that’s a huge fish.’

Silio was on his way back from a fishing trip with his two sons, his friend Ollie and his boy when they saw the giant creature near Mumbles Pier, Swansea.

6ft sunfish spotted by family off coast of Wales

Sunfish are considered one of the world’s heaviest bony fish (Picture: Sililo Martens)

He stopped one of his sons from jumping in in case it was a shark, but they later found out it was an ocean sunfish.

Also known as Mola Mola, they are harmless to humans but are often curious and swim up to divers.

They can weigh 1,000kg and are considered to be one of the world’s heaviest bony fish.

Sharks are classed as a different type of fish as their skeletons are made of cartilage and connective tissue, which is much less dense than bone.

6ft sunfish spotted by family off coast of Wales

They can grow 11ft long and their fins mean they are mistaken for sharks (Picture: Sililo Martens)

Sunfish can grow up to 11ft in length, and Sililo says the one they saw took up ‘at least a third’ of his 18ft long speedboat.

They typically live in tropical waters, but last week one was spotted off the coast of Dorset.

Their name refers to its habit of basking in the sun near the ocean’s surface, which might be why one of them came right up to the boat on Wednesday.

Sililo used to live in the tropical Pacific island of Tonga but had never seen anything like this during his 20 years in the UK.

Recalling the discovery he told WalesOnline: ‘My son was just about to jump in the water when I spotted the black fin from about 20 metres away.

‘Straight away it looked like a shark fin and when we got closer it looked more like a Dolphin and then, only until we got right up next to it, we could see it was this beautiful enormous fish.’

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