‘’Trieste’’ consisted of a heavy crew sphere suspended from a hull containing tanks filled with gasoline (petrol) for buoyancy,  ballast hoppers filled with iron shot and floodable water tanks to sink.
The description of the "Trieste" highlights its unique design features: a large, weighted sphere as the main body, which was used to achieve buoyancy by carrying gasoline (petrol). It also had compartments filled with iron shot for ballast and water tanks that could be flooded to sink the vessel.