Phil or anybody else who wades, if you are wearing waders and fall in turn your body so that you are floating down the river feet first as that way any obstructions will hit your feet not your head. Bring your legs up and slightly bend your knees, the waders will trap the air and as act as buoyancy. If wearing Wellingtons take them off, turn them upside down and force them down quickly into the water. This will trap air in the cavity of the boot, then place one under each arm.