Sea mammals are not an atypical sight around the British Isles, with 36 species of whales, dolphins, seals, and porpoises found in these waters. However, the sight gets pretty unusual when one of these creatures has found its way into the Thames. Especially, like in this case, when it’s a humpback whale.

The humpback whale was first spotted over the weekend near Gravesend about 20 kilometers (12 miles) from central London. Over the weekend, the whale moved closer to London with sightings in the waters near the Eastern boroughs of the British capital.

According to the British Divers Marine Life Rescue charity, the whale was seen “diving and surfacing at approximately five to six-minute intervals, slowly moving down river with the outgoing tide,” The Independent reports. The charity kept a look on the whale for about three hours.

The animal, who is not thought to be in distress or injured, has so far spent a few days around the estuary of the river. People are hoping it will swim out into the North Sea with the tide.  

The English river flows through Oxford, Windsor, and London, and sees its fair share of aquatic beasties. Last year, a beluga whale nicknamed Benny spent months in the Thames before swimming back out again. In 2006, a 5-meter (16-foot) northern bottled-nosed whale swam upstream past central London. It was a member of a species usually found in deep water and had lost its way entering the river. The story, unfortunately, did not end well, as attempts to rescue the whale failed and it died in the river.

Adult humpback whales can reach 12-16 meters (39-52 feet) in length and weigh around 25-30 metric tons. Given they are prone to breaching and doing plenty of surface behavior, they are a popular sight for whale watchers.

Humpback whales are found in oceans worldwide (apart from the coldest reaches of the poles) and in a handful of seas, such as the Mediterranean, the Black Sea, and the Red Sea.

[H/T: The Independent]