The Bermuda dock was designed to be careened, either pulled into shallow water or selectively flooded until one side of its own hull became accessible for cleaning. This let the dock maintain itself despite tropical fouling and corrosion. Its ballast compartments also had to submerge and rise in a controlled sequence while supporting a ship's weight. Salt water acted on both the inside and outside of the dock structure, demanding thick material and regular upkeep. A badly positioned ship or uneven flooding could make the entire dock move, turning a small balance error into a dangerous shift of many thousands of tons.
Notable Point · 2:32:47-2:42:57
How a floating dry dock balances and maintains itself
The dock's ability to lift ships depended on careful ballast control, and it could be careened for its own upkeep.