The video shows the collapse modes of a submarine pressure hull, together with the shapes of different pressure hulls, designed to resist the unwanted implosions of submarine pressure hulls, caused by the effects of external hydrostatic pressure. The hull forms include corrugated and tube-stiffened pressure hulls, which were compared with the conventional ring-stiffened pressure hulls. The video also considers inverted dome cup ends; which were shown to be structurally superior to the conventional dome cap ends.