He's since posted two more videos of the whale, saying it hasn't moved more than 200m up or down the river.
Consultant Ecologist & Ornithologist Dave Andrews managed to film the whale, and shared a video on Twitter this morning.
Belugas, also known as white whales, are "one of the most familiar and easily distinguishable" of all whales, according to National Geographic.
"Nobody tell my boss I'm now watching a live feed of a river", one person joked on Twitter.
A beluga whale has been spotted in the Thames, between Gravesend in Kent and Tilbury in Essex.More news: Leonard strikes exactly the right tone in Raptors introduction
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Conservationists had been waiting to see if the "very lost" whale had made it out to sea after it was first spotting Tuesday afternoon in Kent. We could just do more harm than good.
Beluga whales are identified by distinctive white markings and are typically found farther north, the Whale and Dolphin Conservation group said.
"Beluga whales are a species of the icy Arctic - finding one in the tepid Thames is an astonishingly rare event", said Rod Downie, polar chief adviser at WWF, the World Wide Fund for Nature. Picture Fraser GrayPhotographers flocked to try and picture the rare Whale.
Belugas are considered to be very social and usually live in pods. "What this animal needs is space".
However rescue teams were on standby in case the animal got into danger. In January 2006, a northern bottlenose whale caused a splash after being spotted by a man on a train. Despite the best efforts of rescuers, the 18-foot whale died as those in the water rallied to save it. Officials hope it will return to the open sea.