We got an inside look at how the United States Navy trains sailors to work on Submarines during its eight-week course at the Basic Enlisted Submarine School at Naval Submarine Base New London, Groton, CT. Students train to combat worst-case onboard scenarios such as flooding and fires in realistic simulators. They also learn the techniques they must employ if they have to escape from a submarine and ascend to the ocean surface inside a trainer known as the Pressurized Submarine Escape Trainer or PSET. Volunteers for submarine duty go through a mental health screening, and according to the Navy, can be disqualified if they are diagnosed with depression or anxiety disorders - medical issues that don't necessarily disqualify applicants from other roles in the US military. INSIDER spent 6 days inside the Submarine School to observe different classes of students at various stages of training.