The Moray Firth whale's behaviour indicates that it could be dying
"It's like finding a panda in a supermarket," said Mark Simmonds, on the appearance of a sperm whale in the shallows of the Inner Moray Firth.
The Whale and Dolphin Conservation Society's (WDCS) director of science is clinging to a slim hope the huge marine mammal will make it back to deep water.
Mr Simmonds said: "The whale shouldn't be there.
"It is very unusual for a sperm whale to be so far inshore. It is a deep sea animal found further offshore."
The male - measuring 40-45ft and weighing about 50 tonnes - may have been a victim of the southern North Sea "whale trap".
Mr Simmons explained: "This is an area of shallower water and soft muddy bottom which confuses the whales' navigation.
"The whale may have made a navigational error, or is ill. Elderly whales are more likely to make navigational errors.
"It is moving with the tide which we would expect him to do if he was dying and he may die and strand, or strand and die."
But he added: "There is still a chance he makes it out to deeper water.
"All we can do is keep the area peaceful and make sure he is disturbed as little as possible."
Sperm whales hold records for deepest diving mammal, largest toothed whale and largest brain.
They mainly feed on deep sea squid.
The species was the star of Herman Melville's 19th century novel, Moby Dick, which was about a white whale pursued by a vengeful Captain Ahab.