That guy being thrown into a pool is a fully-equipped US Army cadet about to enter their final survival challenge. They call it Survival Gate #4 but they may as well call it The Gate of Hell, because that's how it sounds like:
Weighed down by heavy equipment, cadets must perform several tasks in a pool amid simulated battlefield chaos. Artificial fog, rain, and deafening noise are pumped in, darkness is punctuated only by strobe lights, and the water is churned by artificial wave makers. Since its inception, every graduating cadet has met and mastered the Survival Gate # 4 challenge.
Image by U.S. Army photo by Sgt. 1st Class Christopher Fincham