Of the calls the RNLI respond to every year, some are a race against the tide while others are against the weather. But all of them are a race against time. The crew at Tower, on the River Thames in London, are the busiest of all the lifeboat stations, averaging over 500 shouts a year and aiming to launch to any emergency in under 90 seconds. When a call comes in about a man in the water near the Thames Barrier, they reach him with just moments to spare. In Fleetwood, on the Lancashire coast, a desperate 999 call alerts the crew to a bait digger — out looking for worms on the sand flats — who has been caught out by the incoming spring tide and is in danger of being submerged and swept out to sea. And on the most southerly point of the Sussex coast, in Selsey, the crew race to the rescue of a local diver with a suspected case of 'the bends'.