Photos: explore an underwater park...

In Austria, find one of the world's most unique parks. Warning – you'll need a snorkel to visit.

It might not be the lost city of Atlantis, but Austria's Grüner See is certainly an underwater visual treasure. Most of the year, visitors can walk around the park, over footpaths, bridges, and sit on benches. But every summer, snowmelt from the Karst mountains means the park is suddenly submerged in cold, clear, water. Scuba diver Marc Henauer from Switzerland nabbed these incredible photos – we suggest you dive right in.