The black sea is an inland sea. That means that it is almost completely surrounded by land. The surface waters are 50 percent as salty as the ocean, while the underneath surface water is saltier water, and the two don't mix much. As a result, fish, etc live in sea's upper layers and can't survive below 330 to 490 feet because deeper layers lack oxygen. And, because deep waters are full of hydrogen sulfide (known as "sewer gas"), these deep waters are home to sulfur, small eating microbes that don't use oxygen to survive.
Ever heard of the "Graveyard of the Atlantic"? Well, Sable Island sits dead center in the middle of it. While the island inhabits over 400 wild horses, scientists have also found that the ocean around it is the site of about 475 shipwrecks! While it has never been permanently civilized, it has been the home to shipwrecked sailors, and even pirates!!! It was declared Canada's 43rd national park on June 20th, 2013.
There is 2000 to 5000 snakes estimated living on this 106 acre island. This is probably the feature that makes it not appealing and very forbidden by the Brazilian Navy to anyone other than scientists. The most venomous snakes in the world is the sole snake inhabitant, the Golden Lancehead Viper.