Test Depth: NOUN. The depth at which a US Nuclear Submarine is certified to dive to at any given time. Generally this is a depth not reached on a regular basis. It is only attained rarely, and not under normal circumstances. If done so under "normal" circumstances it is only after careful preparation. Test Depth is roughly 2/3 crush depth.
Nervous NUB: Are we really going to test depth today?
Salty Dog: STFU you useless POS! Ain't nothing to be afraid of, hell I got more time on a shitter at test depth than you have on this boat!