After he pitched down the nose, the pilot watched his airspeed indicator, waiting for it to show the plane gain speed. That's because he thought he was traveling at the 170 mph "stall" speed of his indicator; actual speed was approximately 500 mph!
From an altitude of 1800 feet, the plane descended at 45 degrees. At a supposed "stall" speed of 170 mph, the pilot knew he had at least 12 seconds before the plane struck the water, but that airspeed would start to recover in just one second. After one second, maybe two, he'd raise the nose. But the stick shaker never stopped, because of the faulty indicator; meanwhile the real speed was a normal 500 mph.
Eyes on the indicator, in 3 seconds the pilot flew into the ocean.