Navy divers are called to rescue a group of office workers trapped in a basement under floodwater in Leeds, UK. The only access to the basement is via a 1.5 x 1.5 m horizontal hatch which is currently under 1.8 m of water. The hatch is hinged on one edge, with a solidly built brass ring handle at the other end. The divers try to pull it open, and soon realise they will need a crane. What minimum lifting load should they ask for? What mistake are they making?