Bob,
By no means an expert on submarines ,but, if I recall my childhood education,there is a limit to how high a Boat can be ballasted up,for stabilty reasons , especially in rough seas.Most come up just high enough for the conning tower to be fully exposed and a little bit of the upper deck.
A winching ops off of the conning tower is preferable to that on the exposed deck for obvious reasons. In my previous life, I spent a few hours transferring supplies and people on and off Boats by Seakings and Alouette 3s and don't recall a single instance when we had such rough seas. BZ to the crew of this particular mission.
Alt 3.