caisson

An enclosure from which water can be expelled, in order to give access to underwater areas for engineering works etc.
The gate across the entrance to a dry dock.
A floating tank that can be submerged, attached to an underwater object and then pumped out to lift the object by buoyancy; a camel.
A two-wheeled, horse-drawn military vehicle used to carry ammunition (and a coffin at funerals).
A large box to hold ammunition.
A chest filled with explosive materials, used like a mine.
A coffer.