Giethoorn is a village in the Dutch province of Overijssel. It's known as "Venice of the North" or "Venice of the Netherlands". There are absolutely no roads and all transport is conducted by water over one of the many canals.
World's deepest swimming pool: Plunge into Y-40 Deep Joy in Italy
Jason de Caires Taylor’s underwater sculpture garden in Cancun. Constructed out of concrete and steel, and bolted to the ocean substrate, the works here act as artificial reefs that provide “an ideal habitat for filter feeding organisms.” http://www.dedeceblog.com/2010/10/13/cancun/