Martin wrote:

What would be the best thing to
do in such a scenario - open all door prior to 'landing', highest angle of
attack you can get, and set down on the water?

Open the doors. If possible, lock them so that they will not close again when the
water hits them. Do a fairly normal landing, keeping the speed down and the nose up.
Keep the speed up enough to avoid stalling the aircraft. Keep your seatbelt fastened;
about the worst thing that can happen is for you to get thrown around and lose
consciousness. If there are substantial waves, land across them. The best place to
set it down in this case is the back side of a wave, but, as Ernie Gann put it, "Show
me the maestro" who can accomplish this.

Once down, unfasten the seat belt. If the door won't open because of water pressure,
keep your head high to breathe as long as possible and bail out after the cabin fills
enough to get it open. If you find yourself well under water at this point, breathe
out just a tad and follow the bubbles to the surface.

Some people worry that the gear will dig in and flip the plane, but articles I've
read indicate that this rarely happens in real life.

George Patterson
In Idaho, tossing a rattlesnake into a crowded room is felony assault.
In Tennessee, it's evangelism.