Class O Pelagic planets range in age from 3 to 10 billion years old. Their diameters range in size from 10,000 to 15,000 km. They are always located in the eco-zone region of a star's solar system. Class O worlds have an extreme abundance of water covering more than 80% of their surface. They have Class M-like atmospheres, with oxygen/nitrogen and other trace elements. There is almost always life, but almost all of it is aquatic plant and animal life, with little land mass to evolve surface creatures. Sentient races evolving on such worlds are likely to be aquatic in nature.
- Max of 20 Planetary Facilities without pressure domes due to limited land mass.
- Can have Waterport & Fishery facilities.
- Defenders gain bonus when deploying Naval Units.
- Attackers suffer penalty when not deploying naval units. (Limited landing zones for ground units increases vulnerability to counter-attack).
- Certain weather events are increased in effectiveness.