people snorkeling and diving in blue crystal clear glacial water in silfra thingvellir national park iceland

algae american and beautiful between blue clean clear cold colorful crack crystal deep diving drinkable ecology fissure formations freezing geology glacial glacier green healthy hills iceland lake lava liquid marine moss mountains national natural noodles north ocean park people planet plates popular pure recreation reflection river rocks sea silfra snorkeler snorkeling spring stones structure tectonic texture thingvellir tourists traveling two underwater view visibility volcanic wall water wonder