Complex sentence: Enlisted sailors attending sub school will first go through BESS (Basic Enlisted Submarine School), a 8 week program that teaches pupils the rigors of undersea life, such as shoring (patching leaks and ruptured pipes), firefighting, and boat handling techniques.
Split into simpler sentences: Enlisted sailors attending sub school will first go through Basic Enlisted Sub School (BESS), an 8 week program that teaches the rigors of undersea life. BESS includes training in patching leaks and ruptured pipes (shoring), firefighting, and boat handling techniques.