PC Victoria Duthie and her colleague PC Ian Brown were called to look after the grey pup after it was spotted by a taxi driver in the early hours yesterday.
The driver was taking a passenger home in Lerwick, Shetland, when he saw the seal near Tesco.
He called the police who contacted Hillswick Wildlife Sanctuary, asking if they could help, as they did not want to take the young pup into custody.
But with sanctuary owner Jan Bevington recovering from a flu bug, her husband Pete set off on the 35-mile journey to rescue the creature while the police continued to watch over it.
PC Duthie said it was an opportunity to overcome her fear of seals.
She suggested calling it Nicholas, while her colleague favoured Santa.
Mrs Bevington said if it was a girl they should call it Mary. "This is a first for us. We've had Christmas otters before, but never a seal," she said.
The seal is now at Hillswick where it will remain until it has fully recovered and can be returned to the wild.