Keepers Pool may have been deep at one time, but by the late 60's when a few of us from Vesey went there in the Summer, it was very muddy, and only just 6 ft deep in the middle. I CAN vouch for it being cold though !
When I joined the Ambulance service, places like these were often the sites of diving accidents due to lessened depths. Many so-called 'Open Water' sites were also prone to yobs throwing things in throughout the 70's & 80's, so broken glass and supermarket trollies became hazards too.