Yes, sir, only to say that, as the Admiral has pointed out, a submarine by its very nature has a lot of vulnerable fittings external to it. These can be damaged quite a bit by touching the bottom of the sea. Submarines, even in areas that aren't iced, are very careful to avoid shallow waters for numerous reasons. They don't have very much room to manoeuvre, so they tend to stay away from these. Certainly the problem is compounded greatly in areas that are iced, where navigational techniques are much more difficult and the sonar conditions, which enable them to see where they're going, are not conducive to safe and efficient navigation.
On November 24th, 2009. See this statement in context.