If you can't decide between an ocean dive and freshwater, you can do both
According to an older theory of continental drift, the Eurasian and North American continental plates shift and grind together in an endless clash of subterranean forces under a gaping rift at the tip of the Reykjanes peninsula in southwest Iceland. Bjarnagjá is an 18 m deep lava ravine on this very peninsula where the tectonic activity has caused Iceland to rise out of the ocean.
The water in Bjarnagjá is mostly fresh groundwater but it is influenced by the salinity of the sea as the rift is only few hundred meters from the coast. For those who have the appropriate level of training and diving experience this site offers dives in an overhead environment.