The sound of silence shattered by Sannox submarine.

We looked wistfully back at the beauty of Glen Sannox and Sannox Bay and...

...continued north in near silence until we emerged...

...from the shade of the mountains into the last of the day's sun at North Glen Sannox.

Then the peace of the beautiful evening was shattered by a loud, low pitched throbbing, vibrating sound that was coming from this surfaced nuclear submarine out in the Sound of Bute (a recognised submarine training area). At first I thought the noise sounded like a heavy twin rotor helicopter like a Chinook but the arrival of a Sea King helicopter showed that the noise was much louder and lower than helicopter noise. It lasted for over an hour and did not stop till well after darkness had fallen. I have no idea what the noise was. As far as I know nuclear power submarines' engines have no reciprocating parts and they are designed to operate as silently as possible. Perhaps they were testing some sonar warfare device?

Whatever, we did not expect to see any ceteceans on this evening, they are easily disturbed by noise in the water.