 90 miles off the coast of Cuba, under these calm waters, US Army special forces are at work. Welcome to Key West. The first thing I'd say when I jump in that water is thank God it's warm. My mom, I don't tell her much of what we do. Key West is one of the hottest tourist destinations on the planet. Deval Street is where everyone goes, but most don't realize that several miles away is an entirely different world. These students are here for the combat diver qualification course. The class is made of green berets, rangers, and even West Point cadets. The closed circuit system that we use as combat divers, it does not give any bubbles. So there's no trace that you're actually under the surface. Close circuit dive equipment is much more complex than open circuit. And under the water, there's no room for error. They inspect us. They do a pre-dive inspection. And if we have something wrong, that's on us. If a student makes a mistake during preparation, there's no yelling. Just calm, remedial training. You guys are going to be famous, sir. Yeah, perfect. The students, when they first come here and they first show up to the course, they're treated, or they're very much micromanaged. Every little thing they do is dictated. Every little mistake they make is corrected. The instructors are everywhere. They see everything. The first step. I had an extensive background in freediving and growing up on the water, but I knew nothing about combat diving. Previous experience in the water doesn't always help. The most challenging obstacle that I faced since starting the course was the one-man confidence exam. Students must recover after having their ability to see and breathe ripped from them. That's one of the most stressful days I've had at this course. So leading up to that was very, very hard on me. Not everyone will make it through this portion, but those that do say the same thing. You have to remain calm. And I think that's the biggest goal here for us as students is to learn how to remain calm under situations that you don't think you're going to make it out of. The ring of this bell signals he's ready to go home. Every attempt to train, teach, coach, mentor is made. They'll get extra training, anything to help them stay on track. But if somebody washes out, it's because he quit like on himself. There's not a lot you can do about that. He's probably already made his mind up. It takes a special green beret to want to become a combat diver. It requires a self-starter, somebody who wants to accept the challenge of this course. It's a very difficult and challenging course, but one with proper training and preparation, that green beret or ranger will succeed here. From Naval Air Station, Trumbo Point, I'm Petty Officer Glenn Slaughter.