Thanks for all your help guys.
I am certainly not interested in snagging fish and I understand about low water and holding pools.
i have just had a week fishing in Iceland, using a floating line with an intermediate tip and the an add on sinking tip. I mostly used tube flies, some tied on 1" brass tubes.
I caught 63 fish in 6 days, lost about another 50 and did not snag any. The reason for the brass tubes was to get the fly down in fast moving water.