“Officer, I emphatically deny that I played any part whatsoever in the decision to take that engine over that railway bridge. There was I, sitting in the traction truck as a passenger, minding my own business, when I started to notice that we were passing these prohibition signs with the legend '6 tons mean gross weight'...”
If I remember the article correctly, it wasn't the bargees but the board of the Somerset Coal Canal that got trapped in a caisson that started to tip downwards at one end, a process assisted by the free surface effect on the water in the caisson. By the time rescuers had drained the whole lift chamber to get the directors out, the breathable air in the caisson had nearly been exhausted and the directors, once revived, lost no time in abandoning the caisson lift concept.
Where Tim's analogy goes a bit astray is that, unlike the constrained water in a submarine's ballast tanks, the water in the caisson was, in effect, already within the 'crew space' and free to flow in whatever direction gravity might take it.