Michael Dalder / Reuters

Uwe Kiehl of team Germany I dives during a match at the Underwater ice hockey Championships in lake Weissensee in Austria on Feb. 17.

Michael Dalder / Reuters

Thomas Jurkschat and Uwe Kiehl of team Germany I concentrate on the surface before a match at the Underwater Ice Hockey Championships in lake Weissensee in Austria on Feb. 16.

Michael Dalder / Reuters

Team Germany I plays Austria II during a match at the Underwater Ice Hockey Championships in lake Weissensee in Austria on Feb. 17.

Michael Dalder / Reuters

Uwe Kiehl of team Germany I breathes on the surface during a match at the Underwater Ice Hockey Championships.

Michael Dalder / Reuters

Equipment is prepared before a match at the Underwater Ice Hockey Championships in lake Weissensee in Austria.

Underwater ice hockey is played upside-down underneath the ice of frozen lakes with a floating puck by teams of two divers in wet suits and flippers. Reuters photographer Michael Dalder made these unique pictures on assignment covering the Underwater Ice Hockey Championships in Austria.

Dalder, also a diver, wrote about his adventures in Reuters' Photographers Blog:

I’ve been diving for almost 15 years, but due to family matters it has fallen off my list lately. So a new picture assignment at Lake Weissensee in mid-February 2013 just came right to my diver’s heart: The Underwater Ice hockey Championships.

Ice diving is, together with cave diving, considered to be the most dangerous diving discipline. For that reason I listened to the security briefing attentively. Continue reading.