Like visitors at the Four Corners Monument in the southwestern U.S. — where you can touch four states simultaneously — divers at Iceland’s Silfra Fissure can touch the walls of the Eurasian and North American continental plates. You’ll start from the shore of Thingvallavatn Lake in Iceland’s Thingvellir National Park and dive in water that’s seltzer-water clear. Some facts:

1) The glacial water is not only clear, it’s refreshing, which is code for nearly freezing — the water temps are nearly constant year-round, ranging from 2°C / 35°F to 4°C / 39°F.

2) Where does the water come from? It’s filtered meltwater from Langjökull, Iceland's second-largest glacier, through porous underground lava — for 30 to 100 years! — until it reaches the north end of Thingvallavatn Lake.

3) The water is so pure that you can drink it during your dive.

4) Even though Thingvallavatn Lake teems with fish like brown trout, Arctic charr and three-spine sticklebacks, they don’t venture into the fissure.

5) There are three main dive sites: Silfra Hall, Silfra Cathedral and Silfra Lagoon. The best-known and most spectacular section is the Cathedral, which is the 330-foot-long fissure often written about. The visibility there stretches nearly from the beginning of the dive to the end. Silfra Hall leads into a cave system with a maximum depth of nearly 150 feet. Swim-throughs underneath rocks and boulders can be dived here at different depths. In Silfra Lagoon the crystal-clear visibility is amazing. It’s almost 400 feet from the entrance into the lagoon to the other side and you can see all the way across. The lagoon is the exit point for divers and snorkelers.