BUD/S has an attrition rate of between 73% and 75%, the Navy told NPR in 2017.
"So, while it is important to be physically fit when you go through training, you find out very quickly that your background, your social status, your color, your orientation, none of that matters," according to McRaven, who recently wrote the memoir, "Sea Stories: My Life in Special Operations."
"The only thing that matters is that you go in with this purpose in mind and this — the thought that you are just not going to quit, no matter what happens."