A mystery sea beast that’s more than 23 feet long, weighs an estimated four tonnes and has no face will be probed by scientists in a bid to discover its true identity.

The colossal creature was found on Broad Haven South Beach in Pembrokeshire, Wales, last week and reported to the UK Cetacean Strandings Investigation Programme (CSIP).

But with the gloopy remains already decomposing, experts couldn’t make a firm identification and now a sample from the sea beast must be sent for testing.

Matthew Westfield, the CSIP stranding co-ordinator for Wales, said: “It’s very difficult to tell for certain what it is because it’s so badly decomposed.

“It died at sea and had been dead for a while before it washed up on the beach, so it would have come in with one of the high tides.”

BROAD HAVEN SOUTH BEACH, PEMBROKESHIRE, WALES SEA BEAST
Investigators discovered the sea beast after a woman reported 'a blob' washed up on the beach in Pembrokeshire

In pictures from the scene, the remains are seen as a grey husk, stringy in some places, with bony elements showing through in others.

No obvious feature of the creature’s biology stands out, with the head seemingly gone and no limbs apparent.

And though Mr Westfield identified a spine, measuring some 23 feet long, even the animal’s true scale is uncertain.

BROAD HAVEN SOUTH BEACH, PEMBROKESHIRE, WALES SEA BEAST
Scientists have sent samples to the Natural History Museum and London Zoo
BROAD HAVEN SOUTH BEACH, PEMBROKESHIRE, WALES SEA BEAST
The team are working to uncover its true identity

He said: “Basically the whole head element was either decomposed or missing or pointing in the wrong direction.

“We were unable to say, ‘right, there’s the head element of it’ so we suspect it could have been longer.”

However, inspecting the remains in person did offer some clues.

Matthew said: “Basically I got a report of a blob, a huge thing that washed up on a beach.

BROAD HAVEN SOUTH BEACH, PEMBROKESHIRE, WALES SEA BEAST
Some pictures show the remains as a grey husk while others show bony elements

“And the lady that actually reported it to us had done a bit of research and had initially come back saying that she thought it might have been a basking shark.

“Well by the pictures we initially didn’t think so because of the size of it and because it is rare to get basking sharks wash up on the beaches around Wales.

“So initially we thought it was going to be a whale but when we actually got there and did an exam on it, it became clear that it definitely wasn’t.

“The initial clue was the smell of rotten fish. Decomposing fish smell different to decomposing whales.

Experts say they will likely never know what killed the sea beast
BROAD HAVEN SOUTH BEACH, PEMBROKESHIRE, WALES SEA BEAST
Mr Westfield believes the remains could be of a basking shark

“Then we got closer and we had a look at the bone structure which indicated that it definitely was not a whale and it was going to be some sort of fish.”

Mr Westfield now believes the remains to be of a basking shark, but he still can’t be sure.

He said: “We couldn’t say 100% because there are other species it could be, even including the whale shark – which is actually a bit bigger but then it could have been a juvenile.”

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He continued: “We’ve taken pictures, we’ve taken a couple of samples, and we’ve sent them off to the Natural History Museum and some of the specialist teams there, along with London Zoo.

“We just have to wait and see what happens.”

As for what killed the sea beast, that will likely never be known.

Matthew said: “It’s completely impossible to say what the cause of death was.

“It could be anything from its age, to bycatch, to injury to anything else.”

The remains must now be either buried where they are, removed from the beach in chunks or left for nature to take its course.