Documentary looking back on the eight day swim that comedian David Walliams undertook for Sport Relief 2012. Providing the inside story and exclusive behind the scenes access, the documentary takes in all the highs and lows of the outstanding challenge that saw David pass through seven counties, make 111,352 strokes, burn 68,000 calories, battle a serious bacterial infection and even save a dog from drowning as well as enjoy visits from fellow comedians Miranda Hart, Rob Brydon and Jimmy Carr.