This design is common to the subcrustal seas of Ceres, Enceladus, and Europa. Bathyscaphes were also built in the oceans of Earth, but it is unknown whether any survived the Fall. On Ceres and Enceladus, they are generally attached to the sea bed by massive anchors, while on Europa bathyscaphes are normally anchored to the highest spires of a lithodermic reef. Bathyscaphes are built up from clusters of spherical modules and are very similar on the inside to cluster habs elsewhere. Their exteriors, however, are designed for submersion rather than the vacuum of space. Their walls tend to be thicker, especially on Europa, where pressures beneath the planet’s thick crust are much higher than in other oceans. Some are partially water-ﬁlled on the inside, with breathing pockets for neo-cetacean morphs. Airlocks include systems for spraying down those entering to rinse away excess ammonia or salt. Some bathyscaphes supplement reactor power with tidal harnesses designed to convert energy from waves or currents into usable power.
Bathyscaphes are difficult to inﬁltrate from the outside. Technician AIs keep a constant watch for hull breaches. Even if cutting through a hull does not generate an immediate security response, the ﬂooding of the module that results from doing so will normally cause the module in question to be isolated from the rest of the hab.
Not all bathyscaphes are underwater. A few are used by gatecrashers in exoplanet high-pressure atmospheric conditions. These are functionally similar, though without the aquatic focus.