There are beautiful and serene dives—and then there are dives with an added element of danger and mystery so compelling, many will risk their lives for a chance at the challenge.

From New Jersey to Australia, sinkholes, major underwater cave systems and even a military explosives dumping ground, await those who dare to dive. Many have attempted these excursions and, sadly, some didn’t make it back alive. These are the most dangerous SCUBA dives in the world.