The Ministry of Defence police were pictured in Millport Bay earlier this week.
The MOD police boat Iona was seen 'patrolling the local waters' on Saturday by eagle-eyed islanders.
There had been rumours that it might have been TV filming with the second series of BBC drama Vigil filming in Ayrshire. However, the BBC and Police Scotland say they weren't involved.
The News contacted the Ministry of Defence.
A spokesperson from HM Naval Base Clyde said: “The Ministry of Defence’s Clyde Marine Unit regularly visit Millport Bay as part of their routine operations.
"On this occasion the team were conducting anchoring drills.”
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