people do dive the wrecks in Scappa Flow...(sp.?) which..I believe is
somewhere off Scotland?  Right?  Isn't Scotland still in the U.K.?

Yes, and and many Brutish Sub Aqua Club members dive all round the UK!
It's a rather vague question; what exactly do you want to know?
If you are used to warm clear reef dives you may find it a bit
challenging!
Low vis, cold water, square profile often wreck dives are pretty much
the norm.
Most serious divers use dry suits. Ability to use a delayed SMB and
ascend in low vis is a must.