7 Worlds. Elysia

Elysia: an Earth-like rocky planet. Oceanic, archipelagic, and biospheric. Numerous islands of all sizes; continents absent. Tectonics are active but stable. Volcanism is predominantly underwater. Extremely fertile soils and exceptionally diverse flora and fauna with a high capacity for regeneration. No intelligent life has been detected.
Since its discovery, the planet has been declared a nature reserve, with strictly scientific settlements established there to minimize interference with the biosphere and conduct experiments to restore Earth's natural habitats using local samples.