Well I never

http://www.bbc.co.uk/news/uk-scotland-highlands-islands-11605365

Part Quote
An eye-witness said the sub - described as the stealthiest ever built in the UK - appeared to have grounded on rocks.

HMS Astute is believed to have been undergoing sea trials as it is not expected to enter service until next year.

Aside from attack capabilities, it is able to sit in waters off the coast undetected, listening to mobile phone conversations or delivering the UK's special forces where needed.

The 39,000 acoustic panels which cover its surface mask its sonar signature, meaning it can sneak up on enemy warships and submarines alike, or lurk unseen and unheard at depth.

End of Part Quote

I have to laugh. It is so good, it can't detect a rock