A diver exploring the wreck of the famous cargo ship Breda has been reported missing.
The coastguard received a call for help from a dive boat just after 11am on Tuesday.
The 54-year-old diver had become separated from the group while exploring the wreck which is located in Ardmucknish Bay near Oban.
Strathclyde Police said the man, from Cambridgeshire, had been diving with two friends at the wreck of SS Breda when he failed to resurface.
A Royal Navy helicopter from HMS Ganet explored the scene while lifeboat crews patrolled the shoreline area.
Further searches were carried out but the diver has not found.
The Breda was a Dutch steamer which was sank after being attacked by a German plane in 1942.
Graeme Watters, Clyde Watch manager, said: "Coastguard Rescue Officers from Oban carried out a second shoreline search at high water to check again whether this diver made it ashore and but sadly nothing was found.
"A search in the vicinity of the wreck was also carried out by navy divers but nothing was found.
"We do not know what went wrong with this dive but our advice to all divers is make sure you are adequately qualified and experienced for the dive you plan to undertake and that you keep a close eye on weather and sea conditions.
"Personal fitness is a top priority for safe diving and so you should be familiar with new or different gear before planning deep dives.”
The search for the missing diver resumed on Wednesday. SS Breda was a Dutch cargo steamer which was sunk by German bombers during the Second World War.