Isonus, viewed from space.
Isonus is an oceanic planet, located outside the veil of known galactic space (Galactic Federation and Pirate space). The base of operations of former Pirate Commander, Xi'ga E'shan, and his followers, Isonus's surface is but a single massive sea, save for a single, closely wound system of archipelagos. Just as well, it's regular atmospheric humidity is nearly off the charts for that of a planetary body, oceanic or otherwise. And, although artificially introduced, it is one of the very few worlds, to be completely compatible with Metroid habitation, (this meaning that they are able to mature and breed on their own, unlike such worlds as Tallon IV).