mercy flush

— A more usual problem with a hatch is that it was shut too tightly. Rig for dive checks can be done submerged, with sea pressure on the outer hatch. New JOs, doing the check, sometimes forget and shut the outer hatch even more tightly when checking it shut. Subsequently, opening the hatch on the surface can be difficult, even demanding a dive to loosen the hatch. Generally happens only once per career (kinda like a mercy flush over a pressurized sanitary tank).