The Waters was the Monean name for a unique planetoid in the Delta Quadrant composed almost entirely of water. In 2375, it had a radius of six hundred kilometers and held a volume of water greater than the Atlantic and Pacific oceans of Earth combined. The Waters contained a complex ecology, including a giant lifeform similar to an electric eel.
The Waters was inhabited by the Moneans, a humanoid species who discovered it in the 21st century. Their population numbered over eighty thousand in 2375. However, since their colonization of the Waters, the containment field holding the planetoid together had begun to degrade. The Moneans predicted that the ocean would entirely dissipate by 2380, but were unable to determine the cause as their vessels were unable to dive more than a hundred kilometers.
The Moneans had several theories regarding the origin of the planetoid. Monean clerics taught that the ocean was a divine gift from their Creators to protect and sustain them, while their scientists believed that the ocean coalesced naturally in a way akin to a gas giant.
The true origin of the Waters was discovered in 2375 by Tom Paris, Harry Kim, Seven of Nine, and Riga, who took the Delta Flyer into the ocean's center. The ocean had once been part of a landmass, a planetary ecosystem inhabited by an advanced civilization. A hundred millennia ago, they launched a field reactor into orbit and used an elaborate kinetic transfer system to move all the water and everything in it into space. This massive undertaking took almost two hundred years.
The Delta Flyer also learned that the containment loss was being caused by the Moneans, whose oxygen refineries were increasing the density of the ocean. This increased the pressure on the reactor, which was diverting energy from containment to its structural integrity field. Captain Kathryn Janeway of the USS Voyager offered to share oxygen replication technology with the Moneans so that they would no longer need to extract it from the water, but in order to save the ocean the Moneans would also have to immediately shut down some of their refineries.
At the time, the Monean Maritime Sovereignty was unwilling to make the drastic changes called for by the Delta Flyer's findings. Concerned for the future of the Waters, Tom Paris and Riga attempted to destroy the refineries, but were stopped by Voyager. The fate of the Waters remains uncertain. (VOY: "Thirty Days")