Silfra is one of the top dive sites in the world and situated in the UNESCO World Heritage Site, Thingvellir, only about 50 km from Reykjavik. Silfra is a freshwater fissure about 60-63 meter deep, where you can almost see end to end as the water is so clear. The water is so pristine it feels like flying.
By snorkeling in drysuit you will get protection from the cold water if the fissure as the drysuit is constructed from layers of insulating fabric. However we always recommend you rather to take the wetsuit as you will have so much more fun.