It amazes me that they can build a ship that large but provide such a small landing area. VLCC's & ULCC's don't move at all when loaded, so don't worry about pitching decks. They are extremely stable, even in heavy seas. When empty, they present a huge surface area to the wind, so they may rock side to side to some extent in high winds. The heliport on a supertanker is normally on the port side just forward of amidships, & usually clearly marked. There may or may not be a landing area on the starboard side, but that is often a winch-only area. I have seen a cantilivered heliport on the stern of one ship, but only one. That should be the requirement - it's wonderful compared to the forward landing area, which has one way in & one way out, & that's mostly downwind, especially if lightering, since the VLCC takes the daughter tanker on the starboard side, & makes a lee for it so there is less movement between the ships. Thus, you mostly land downwind, into a very small, highly obstructed area, & there are lots of skid obstructions, hatches only a few inches high but enough to bend the skid if you land on it. I have refused to land while the tanker was in its current configuration, because there was too much tailwind component. The captain didn't want to turn, but when I explained that I was taking his relief back to the shore, he changed his mind.
Be very careful, but it's not usually that difficult. I haven't landed a 206 on a tanker in some years, but I've been landing S76's & B412's on them, & if the area is big enough for a medium, it's easy for a 206. Some areas are really too tight for a 206, though, so take it slow on the approach & make sure you see everything.
