Lol,plenty of speed where I was Ian,the river narrows(yes,narrows,lol)to probably 7m and pushes hard with boils,the clarity however is like tap water,around three and a half feet deep,you can see every piece of gravel,every blemish on fish,scale damage etc,even more so than summer,making the fish very aware of your presence,i've said elsewhere,but if this river is any reference to barbel behaviour elsewhere(which it normally is fairly standard),barbel are continually flitting from spot to spot,now,they must be looking for food,as if they were running scared there are many inaccessible places they could hide in,when these fish,come through they seem to assess the safety of eating in a spot,then wheel and carry on their way,thus where you choose to place a bait is critical,where I fished was just short of an overhanging clump of reeds(eight rushes)laying on the water on the far bank,so I couldn't see any fish,hopefully they fed because they couldn't see me....
As an aside,in the swim upstream was a fella float fishing(with an old Normark daimura blank,12' 6" and a pin) he had had a long break from the sport and by his own admission he hadn't much angling prowess,he cast a pin fairly well however(his swim was perhaps 13/14m wide),he had some gorgeous casters and his feeding was hit and miss at best,but in the 2.5ft of clear water I could see roach and barbel feeding in a back eddy,some quite large,a large tench visited him several times,I take it his control let him down because apart from odd roach and dace he hooked no bigger fish,yet on the three occasions I went up for a chat they were feeding with gusto on his tasty offerings...
You can see the fish without polaroids,unless light levels are poor,and I mean really see them...