While much of under-ice diving is similar to regular diving, there are a few important differences. First, the divers wear drysuits instead of wetsuits. These dry suits are sealed at the wrist and the neck and don't let any water in beyond the seals. Second, under-ice diving is usually performed using compressed air, not other mixed gases and the regulators used are specifically designed to be used in temperatures below freezing. Most different from regular diving operations, under-ice divers are tethered to the surface. Video footage courtesy of Shawn Harper, The Hidden Ocean, Arctic 2005 Exploration, NOAA-OE.