That video is from a rescue mission. In this footage, the pilot was dropping off crewmen just rescued from a drifting fishing boat. The seas were too rough to land the helicopter on the back of the ship (a USCG cutter), so they lowered them down, but had to do this insane hovering! I just saw this on the History Channel on a program about Alaska. I suspected I could find the clip on youtube, and here it is. Amazing stuff.