A harbour porpoise has been spotted swimming in the Thames.

The aquatic creature was seen frolicking in waters near Gravesend Town Pier yesterday afternoon.

Local photographer Fraser Gray, captured the porpoise on camera whilst out taking photos of ships.

He said: "I'm interested in the river because I photograph the ships and the weather so I had got my camera set up and I was watching a C02 tanker called Helle which was arriving into Gravesend.

"It was going around the stern of the tanker when I saw like a black lump appear on the water with some ripples and then I realised I was lucky enough to be seeing a dolphin or porpoise."

It's not the first time Mr Gray has been fortunate enough to spot the majestic creature in the wild.

The aquatic mammal – understood to be a harbour porpoise – is thought to be a regular visitor to the pier and has been sighted on several occasions.

"It does seem to happen quite often between Gravesend Town pier and the Tilbury landing stage," he said. "Always a single one between this area. Probably he or she is a regular visitor.

The lensman said there was lots of marine life to be spotted in the Thames for those who are patient enough.

"If you watch parts of nature for long enough you get rewarded," he added.

Harbour porpoises are often confused with dolphins and are relatively small in comparison.

Sightings are fairly common in UK waters and the marine mammals often be spotted close to shore in shallow water, either alone or in small groups.

But populations do face threats from water pollution including litter and plastic, noise from shipping, and fishing nets which they can become entangled in.