One thing that all special units have in common is an aversion to quitting and quitters. The greatest sin, the one unforgivable error, is to quit, no matter what the obstacle. Only death can stop a truly determined man. You have to know that the man next to you will not break and run when things get tough.

While not a part of the Special Forces pipeline, the Combat Diver Qualification Course, or CDQC, at the Special Forces Underwater Operations School in Key West, Florida plays a big role in SF culture and lore.

I went through CDQC before it was a seven-week marathon. My hat is off to those guys who took the course after I did. The drills have changed, but the objective remains the same. If you have any trace of claustrophobia or fear of drowning, the clever instructors will find it. They will push that button again and again until you ignore it or quit. There is no try. Every man in my class who failed to graduate quit in pool week. In Ranger School, there were hours and miles between meals where you thought about nothing but how powerfully hunger sucks.

Here is my simple question to you: Would you rather go without a meal for a day, or without a breathfor two minutes? The brain has special circuits to warn you that you are dying and cause panic. Key West teaches you to turn them off. That is what killed Chuck.

The first week, they issued full open-circuit gear, complete with twin 80-cubic-foot tanks. While we got plenty of experience donning and wearing these primitive behemoths, we did not turn on the air and use regulators until week two. My least favorite exercise was bobbing, where you jumped up from the bottom of the deep end with your fins on your hands, got your head above the surface, took a breath and went back down. Repeat until told to stop. The purpose of this drill was explained several times, but the story was never the same twice and none of them made any sense. I did this correctly only once, on test day. But that is not what killed Chuck.

There was another drill called crossovers. Half the class lined up on each side of the long axis of the Olympic-sized pool. At that point, there were about 25 guys still in the class. They pushed us into the deep end so everyone was crowded. Everybody wanted to get as far from the wall as possible, but when they put you in, you couldn’t move that way because you didn’t want to screw your buddies, so there was a natural rotation. If the cadre thought you were sliding down, they would direct you over to the wall.

With Twin 80s, BCD vest, mask, fins, and weight belt, we clung to the edge of the pool. On the cadre’s whistle, you let go, pushed off and swam underwater to the other side. One side went low and the other went high. The low guys tried to stay as high as they could so they used less energy. The perils of this drill included running head-on into an opposite swimmer, causing both of you to lose all momentum or having the guy next to you take your mask off with his push-off arm stroke.

The cadre with the whistle controls the pace. He could drive you as far into oxygen debt as he wanted. We almost cheered every time somebody lost a mask because they had to swim down and get it, and we all got an extra breath. The secret was to remain calm and breathe deeply with the time you had. Hyperventilation prior to diving depletes carbon dioxide in the system, leaving a diver susceptible to shallow-water blackout. There is no warning sensation, and victims typically drown quietly. The cadre were very familiar with shallow-water blackout and watched for it constantly. There was a designated safety officer who counted heads and made sure everyone came up.