During my short time on Valley pool back in 2014 I corresponded with one of the divers Joe Flammia who filmed an underwater session on the water. Joe kindly passed on to me all the footage and pictures they took on that dive and in return i turned it into a film, Valley Pool underwater (https://thecarpcatcher.co.uk/thecarpcatchers_blog.php?post=163).
The dive took place in January 2013 with a water temperature of 5 degrees C and so most of the carp were sat on the bottom hibernating, although interestingly i was informed that many woke before they got near.
Valley pool is an old 'clinker pit' first dug for it's chalk marl in 1888 and typical of the chalk pits around the south-west borderlands of Cambridgeshire it's deep and gin clear.
Despite all the usual problems associated with pits like these and the the snags I had a great time and caught some lovely fish (https://thecarpcatcher.co.uk/thecarpcatchers_blog.php?post=65).
Once the pit became disused in 1934 it flooded leaving all the debris of marl extraction behind it.
You know the old saying, "Thar's a railway line and train at the bottom of that thar lake" well there is in this one, almost.