A humpback whale, moving with the tides between Woolwich and Gravesend, is believed to be the first of its kind in the River Thames for 10 years.
Experts have said a humpback whale in the Thames is not in grave danger, despite concerns it could become stranded in shallow waters.
The 30-foot whale was spotted on Monday at Greenhithe, but welfare teams claim it is not yet in serious trouble.
Julia Cable of British Divers Marine Life Rescue said the whale ‘is not doing anything out of the ordinary’, apart from the fact it is swimming in the Thames.
‘It is not stranded and, as far as we are aware, it is swimming west on the high tide and east on the low tide,’ she told The Times.
It is believed to be the first humpback whale in the Thames for 10 years. The last time a humpback in the Thames was spotted in 2009, also along the Kent stretch of the river.
The whale survived for two days before becoming stranded near the Dartford Crossing, where it was found dead.
Last year the Thames was home to a beluga whale, known as Benny, for three months. It is believed he made his way out to sea after his time in the estuary.
The RSPCA has said it was working with other bodies to monitor the situation of the humpback whale and was ready to provide assistance.
‘We hope the public will behave as considerately to this whale as they did to Benny the beluga,’ said a charity spokesman. ‘It’s important that disturbance is kept to a minimum, to maximise the whale’s chances of returning to the open sea under its own steam.’
Numerous sightings of the humpback, nicknamed Hessy, have been posted on social media.
It is believed he could have swam into the Thames to recover from an illness in calmer waters, or its appearance could be the consequence of a navigational error.
‘We can assume it came into the Thames on the last spring tides at the end of September,’ added Ms Cable said. ‘We will have another set of spring tides in a week’s time, so it might hang about before it goes back out.’
A pair of humpback whales first spotted off the coast of Kerry in 1999 have resurfaced to the delight of