The Ultra Deep Sea is arguably the most alien of the known Ultra Space regions. It occupies an entire universe in its own right and is completely unreachable from Ultra Space by three-dimensional travel. Ultra Wormholes are the only known method of access, and researchers stationed there have collected data that suggests the entire pocket universe is Ultra Deep Sea, with no planets or even outer space beyond whatever sky there may be. Chemical analysis has revealed that the world uses an entirely alien set of elements, but extradimensional visitors are able to survive despite the vastly different substances.
The world strongly resembles an ocean floor, serving as the inspiration for its name. Despite this, there is no evidence of water as we know it; instead, the "ocean" is full of a dense air analogue that can nonetheless support floating creatures. It is mostly breathable by human visitors, but its increased viscosity and nonatomic makeup cause difficulty breathing culminating in chest pains and bouts of unconsciousness. Filtering to the tropospheric pressures of Earth or Astreyza greatly slows the progress of symptoms, allowing a human to inhabit the space safely for up to two weeks. Breathing the "airwater" unfiltered begins to cause symptoms as early as three days of continuous inhalation. Long-term symptoms have yet to be ascertained.
Based on this data, it has been hypothesized that Ultra Deep Sea as a whole is far less dense than any world previously explored. Light from distant sources and differences in biodiversity at shallower depths imply the presence of a surface similar to oceans as we know them. One hypothesis suggests that the low-density environment is the result of a vacuum metastability event in the ancient past, but the hypothesis has been discredited based on the presence of visible light, a similar range of energetic potentials to that of spacetime which supports atomic matter, the lack of instantaneous annihilation of atomic matter on contact with the world's spacetime, and the ability of alien organisms to survive in such conditions. Gravity, the Pauli Exclusion Principle, familiar force-carrying bosons, and light speed limits continue to apply.
Once the creatures of Ultra Deep Sea are thoroughly understood, the Divers' mission will shift to reaching the surface by the least environmentally damaging means possible.
Assigned Squad: The Divers
Halodule, Squad Captain, Communications Specialist
Cyanidia, Senior Researcher, Senior Chemistry Specialist
Volvox, Researcher Emeritus and Physics Specialist (considered lost)