A Beechcraft B200 King Air, operated by LifeMed, impacted the waters of the Bering Sea after becoming airborne from runway 31 at Unalaska-Tom Madsen Airport (DUT/PADU), Alaska. The airplane ended up 400 or 500 yards offshore in the waters of Unalaska Bay near Hog Island and sank. The three occupants were rescued. According to the pilot, after checking the weather on the Automated Weather Observing System (AWOS), he completed the before takeoff check list, back taxied for a runway 31 departure and initiated the takeoff roll. He said he recalled the winds being reported as 100ø at 9 knots. As the airplane accelerated down the runway, he said the airspeed was about 75 knots at midfield and increasing. When the airspeed reached about 90 knots, he applied back pressure to the control yoke to initiate the takeoff and noted a brief positive rate of climb, followed by a sinking sensation. The airspeed rapidly decayed, and the stall warning horn sounded. In an effort to correct for the decaying airspeed, he lowered the nose and immediately noticed the airplane’s lights reflecting off the surface of the water. He pulled back on the airplane’s control yoke and leveled the wings just before impacting the ocean waters. A tailwind takeoff was performed since IFR takeoff minimums and (obstacle) departure procedures only allow for night departures off of runway 31.