Flashbulbs do have their place though, as they have a greater light output and the longer duration of the light pulse makes water look less frozen. Preparation has to begin well before the caving trip. Cameras and lenses are best left overnight somewhere nice and warm. This helps to prevent lenses misting up as soon as they are exposed to the cold damp air underground. Equipment is usually packed in army surplus ammunition boxes, lined with protective foam.
Ammo boxes are damn tough and water proof, their only disadvantage is their weight.
As you can see from the shot below one advantage is that they float so it isn't too onerous dragging them through very wet passages. A set of prints after the trip works wonders, as does buying an extra round in the pub after the trip. Wensleydale Just getting there can be a problem. A waterproof camera box is essential. Once beyond daylight underground, flash guns provide the only practical form of illumination in British caves and mines.