A man walking on a Sussex beach has captured a video of what he thinks is a shark.

Grant Henderson, from Lancing, was taking a stroll on Lancing beach when he spotted what looked like a large fin protruding from the water.

Dr Valentina Scarponi, lecturer in ecology and animal biology at the University of Sussex, said: “From this video alone, it’s tricky to tell exactly what this might be, but it’s concerning that it doesn’t appear to be moving.

“As it looks close to the shore, in shallow water, it could be a smooth-hound shark – an endangered species which can be found around the UK.

“There are approximately 30 species of sharks in UK waters though, so from this video alone, it’s hard to say for certain.

“Seeing a shark up close in nature is a remarkable experience and they are extremely important for the health of our oceans.

“Evidence shows that healthy shark populations help maintain healthy marine ecosystems, which benefits all of us.

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“I hope that with more understanding and experience, there will be a switch from fear to respect and protection, as most species are now threatened with extinction from exploitation.”

However, Richard Cobden from Sussex Wildlife Trust cast doubt over the sighting.

He said: “This looks like a seal, probably a grey seal.

“The head of a resting grey seal can be mistaken for a shark's dorsal fin. This is because when seals are resting at sea, they bob around in the water with only their head or back above the surface.

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“This is called ‘bottling’.”

A smooth-hound shark previously washed up on Lancing beach in August of last year.

Typically feeding on crustaceans and shellfish in the sand and shingle on the seabed, smooth-hounds spend much of their time near the coastline so are vulnerable to being washed up in windier weather.

Sussex Wildlife Trust warned that washed-up marine creatures, alive or dead, should be reported to the relevant authorities.

Andy Fry, the trust’s wild call officer, said: “If you happen to find a stranded marine animal, make sure to give it some space and report it.

"Live animals should be reported to British Divers Marine Life Rescue, and dead animals to the Cetacean Strandings Investigation Program.”