Euthanasia is "absolutely not an option" for the young fin whale which has become trapped at Baltimore harbour in Cork.
The 16 metre-long mammal, believed to be an adolescent female, swam into the harbour at low tide yesterday morning and lay at the bottom of the pier.
Hopes that she could be helped back to sea faded as it became clear that she was injured and starving.
The whale is too large to be put down and nothing can now be done to save her.
Padraig Whooley of the Irish Whale and Dolphin Group has advised spectators to stay away.
"The advice is, especially for people with young children, best not go down because the situation is not pretty and it is actually quite distressing not only for children but for adults as well," he said.
"Unfortunately, again, we are helpless to intervene, just because of the size of the whale, and euthanasia now is absolutely not an option."