A rare beluga whale reported to be swimming in the Thames could be "in trouble", conservationists have warned.
A beluga whale has been spotted in the River Thames, shocking onlookers.
The RSPCA animal welfare group said it was "working with other agencies to monitor the situation".
Describing the Thames whale as "vulnerable", Dolman explained that noises from nearby and passing boats may alarm the animal as it attempts to make its way out of the Thames and back home to the Arctic.
Two beluga whales play together.
The rare marine mammal, nicknamed Benny, was seen near Gravesend yesterday and appeared to be swimming strongly and feeding in the estuary.
The last sighting in United Kingdom waters was in 2015 when they were spotted off northeastern England near the Northumberland coastline, but they left shortly afterwards, she added.
"We do have quite a lot of plastic bags, which could be quite an issue", she said.
It said it was ready to provide help to the whale if asked to do so by other agencies.
The video has since been viewed more than 160,000 times, sparking "River Thames" to trend on Twitter.
"We're hoping if we give it enough space and keep an eye on it, it will find its own way out of the Thames to an environment that's more appropriate for it".
In 2006, a whale died after it swam up the river into central London despite rescue efforts.
"As I live in Gravesend I had no choice today but to literally run to the River Thames to watch the Beluga Whale".
They range from 13ft (3.9m) to 20ft (6.1m) in length and have distinctive rounded foreheads. They are known for living long lives and are typically found further north, in Arctic waters. They can move between salt and fresh water.