Underwater ice hockey (also called sub-aqua ice hockey) is a minor extreme sport that is a variant of ice hockey. It is played upside-down underneath frozen pools or ponds. Participants wear diving masks, fins and wetsuits and use the underside of the frozen surface as the playing area for a floating puck. Competitors do not utilize any breathing apparatuses, but instead surface for air every 30 seconds.
It is not to be confused with underwater hockey, in which the floor of a swimming pool and a sinking puck are used.