US Navy/PO1 Abe McNatt For aspiring Navy SEALs, the selection process, known as Basic Underwater Demolition/SEAL (BUD/S), is a six-month series of challenges for their skills and endurance. Maybe the most trying period is "Hell Week," a six-day gauntlet of constant exertion that shrinks their ranks and reveals what they're made of. Basic Underwater Demolition/SEAL (BUD/S) training is a six-month selection process and the gateway into the Navy's SEAL Teams. Broken into three phases (First Phase, Second Phase, Third Phase), BUD/S has an attrition rate of between 70% and 85%. The complete SEAL pipeline attrition rate — from the moment someone walks into the recruiter's office to the end of advanced qualification training — is over 90%.