7 Worlds. Aquaria

Aquaria: an oceanic planet, a satellite of a gas giant with a ring system. Its unique feature is the absence of tidal locking. The surface is covered by a deep ocean, with minimal land masses, consisting of isolated small islands or rocks. The ocean's biosphere is very rich and multilayered, with vegetation present.
A highly developed technological civilization was discovered in the ocean, with which contact was successfully established. By agreement with the Aquarians, the humans established strictly limited scientific bases here to study the planet and facilitate further contact between the two civilizations.