Royal Navy Bomb Disposal experts are making their way to Orkney after a torpedo was discovered in Scapa Flow.
Shetland Coastguard was alerted to the find at 1.45pm.
A spokeswoman for the coastguard said Orkney Harbour Authority was investigating the incident.
She said: “It is suspected to be a WWII warhead from a torpedo. Royal Navy Bomb Disposal experts have been informed and will arrive in Orkney on Thursday morning to deal with it.”