I have seen a Sea King do that once, and as I recall it rolled over and sank!
I know the fuselage on those things are supposed to be watertight, but I can’t recall even seeing a picture of one doing it-that said, I defer to you, since you sound like you have experience in that area...:)
No experience as a pilot or rotorcraft engineer, but I work with a lot of people who do have that sort of experience.
If you look at pictures of the fuselage of an H-3 Sea King, you will see that it has a little "keel." Those big sponsons are also not just to hold the landing gear -- they help keep the aircraft upright in the water.
I am sure they are very ungainly boats -- the H-53s as well -- but they are indeed designed to be amphibious. Just do a google image search for sh-3 on water and you will see plenty of pix of Sea Kings, rotors stopped, bobbing along like nobody's business haha!
Here also is a floating H-53. The image caption calls it an H-3 but it is definitely a 53. They are also calling it an echo model and I think it's a D!
