Beluga whale spotted swimming in the River Thames in shocking video

Two beluga whales play together. (Tyson Paul)

A beluga whale has been spotted in the River Thames, shocking onlookers in South East England.

Ecologist and ornithologist Dave Andrews posted a video to Twitter expressing his surprise that the mammal, known for living in the Arctic and sub-Arctic, was swimming in the river near Kent.

"Can't believe I'm writing this, no joke - BELUGA in the Thames off Coalhouse Fort," Andrews wrote on Twitter.

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He followed that up with subsequent tweets about the whale, including its location and its feeding habits.

The British Divers Marine Life Rescue said the presence of the beluga is "concerning as it's not a common species, however it's swimming strongly and feeding," according to Sky News.

Officials are asking the public not to get close to the whale, which was reported to be in the Gravesend area in the county of Kent.

The River Thames, one of the longest rivers in England, runs through several major cities and towns, including London, Oxford and Windsor.

Beluga whales are considered "near threatened" by the World Wildlife Fund, with a population of over 150,000.

They are considered "extremely sociable mammals" and live in pods. They are known for their bulbous forehead, known as a "melon,” which allows them to make various facial expressions due to its flexibility.

Belugas are able to produce sounds such as chirps, clicks, whistles and squeals, which has given them the nickname "the canary of the sea."

The Associated Press contributed to this report. Follow Chris Ciaccia on Twitter @Chris_Ciaccia