What some people probably don't understand is that alpha-protect is not a normal flying state to be in. It is unthinkable to intentionally enter alpha-protect during an approach to land or ditch. Alpha-protect is a last ditch effort (by the aircraft and no pun intended!) to prevent a stall.
KayPam, Sully did not 'exactly know what he was doing'. He thought he was flying above VLS, i.e. above normal safe approach speed. But in fact he was far, far, very unsafely far below. Read the report. Again, no criticism, just facts.