the.com/submarine
a steel held breath that hides entire cities of men beneath the crushing dark
means A watercraft designed to operate underwater, especially a warship that travels and attacks while submerged.
from From Latin 'sub' (under) and 'marinus' (of the sea, from 'mare,' the sea) — literally 'under-sea.' English used 'submarine' as an adjective for undersea things from the early 1600s; it hardened into a noun for the vessel itself in the late 19th century, as inventors finally built craft that could dive, hide, and surface at will. The same 'mare' still tides through 'marine,' 'mariner,' and 'maritime.'
endurance limitnuclear subs surface only when food runs out
silent depthsome dive deeper than most jets fly high
hidden fleetcan launch missiles that end nations from underwater
first killa hand-cranked sub sank a ship in 1864
crush pressurea hull breach at depth implodes in milliseconds