The control stem drops the water, gas goes through the filter. Electric lights fail, too much humidity. Green is the best, blue and red are available. Spelunkers won't tell you about caves unless you look like a spelunker. Knee pads essential.
Metal rusts quickly in a cave.
Bring spare tips and cleaning wire as tips burn out, always carry three spare tips. Wear knee boots over shoes or hip waders. A long sleeve heavy shirt is needed as air is 56-58 degrees and water is 50 degrees.