The school swimming pool opened in 1968, following two years’ of fundraising by staff, parents, pupils and Old Portmuthians which included a raffle, barbecues , a cheese and wine party, a firework display, Christmas Fayres, carol singing events, individual donations and £100 from the OP Club. The Lower School Headmaster, Mr Keall, believed to have been dressed in a top hat and old trousers, was thrown into it by 50 pupils during the opening ceremony, closely followed by a teacher in a tracksuit and wristwatch who was not expecting a dunking. The photo shows Mr Keall in the pool, though he appears to have replaced his headgear, presumably for health and safety reasons. 

The pool has been described by OPs as "character building" at best, but more commonly as "freezing" and "a melted ice rink". One OP said he "loved swimming but hated that pool". Another that he'll "never get over the freezing walk back to the changing room once we got out". 

The pool was enclosed and a roof put on the following year following concerns about the low temperature of the water, clogging by leaves, pollution from the nearby power station, vandalism and of “intruders using the pool”, probably local children from Portsea. The roof was paid for from the Professor Nock Fund drawing from a large legacy left by Arthur Darby Nock (OP classicist and theologian who was a professor at Harvard University). The sunken pool was opened in 1995.