Rescuers hope a sperm whale washed up on a beach in Norfolk will die overnight to end its suffering.
British Divers Marine Life Rescue (BDMLR) said the creature became stranded at Hunstanton early on Thursday morning.
High tide arrived at the beach at 2.50pm, engulfing the whale but it was unable to move.
Even if it were to return to the sea, it is likely to become stranded again and would almost certainly die, the BDMLR added.
Stephen Marsh, operations manager at the BDMLR, said there is nothing the volunteers can do due to the size and weight of the whale.
He added: "This is not a rescue operation, it is just about making the whale as comfortable as possible.
"We hope it will die at some point tonight because it is suffering a lot at the moment.
"Usually sperm whales die fairly quickly after coming ashore but it could be 12 hours, it could be more."
Kieran Copeland, from the Hunstanton Sealife Sanctuary, which is helping the rescue attempt, said possible internal injuries mean the whale is unlikely to survive.
"It is still alive at the moment but the prognosis is very poor. It is very unlikely to survive," he added.
It comes after three dead whales washed up on the Lincolnshire coast and one was found at Hunstanton last month. It is the 29th stranding across Europe in the last two weeks.
The whale is said to be 1.5 miles out on the sand and the coastguard is also in attendance.
Mr Marsh said earlier: "There's nothing we can do, it's likely to be between 25 and 30 tonnes. We can't lift it, we can't roll it, the vets can't put it out of its misery.
"The body will be breaking down and releasing toxins, causing organ failure. It's a very sad case but we will have to let nature take its course."
Mr Marsh said strandings can happen naturally and the recent increase might be due to a rise in whale populations.
"It will get more attention because it's a big animal but strandings do happen naturally, and we are just not used to seeing them as we decimated the population through whaling," he said.
"The females and calves stay in warmer waters and the males leave as they become sexually active and form bachelor pods. They will then go back to the warmer areas on an annual basis to mate.
"We don't know if they were trying to migrate down to the tropics, but there's no sign yet of any man-made activity that would cause them to come in, but that is being investigated."