Mo'ia Atoll is an atoll located in Southwestern Manoa Lai. It contains a set of ruins, which are home to stone carvings and unique marine life. Before you receive word about the ruins through an email, you cannot swim through, due to an unnaturally strong current, and you actually have to grab onto the passing Whale Shark that swims into the Atoll (and from then on out lives there).
Some of the passageways are also blocked by unnaturally strong currents (making going down them a one-way trip), but as it turns out, these currents are caused by ancient mechanisms spouting water at a high enough pressure to sweep the player away and not be able to swim against it, hence the one-way trip.
Central hall is, as its name suggests, in the center of the ruins. The Hall is home to some smaller fish, but the main attraction here is the only pod of Bottlenose Dolphins in the game. Along with this, a dead-end tunnel located near the bottom of the Hall leads to one of six Stone Monuments situated all around the Ruins. One of the one-way hallways leads into the Hall.
The inner section of the ruins is given a slightly eerie feeling by the haunting music change that occurs as you enter, along with the holes in the ceiling shedding sparse patches of sunlight onto the floor and the mazelike configuration. The only two rooms whose names are known are the Room of Oracles and the Prince's Room. There are two one-way hallways, one of which leads into Central Hall and the other of which leads to the room prior to the Prince's, the room with the hole in the ceiling.
The unique life here includes the resident Asian Sheepshead Wrasse, who greets the player as they enter the ruins, the 2-3 Atlantic Tarpon in the second to last room, and the Beluga, after unlocking it,
The three treasures found in the Atoll are the Deity Idol and Inscribed Nephrite, both in four scattered pieces, and the Life Beads, which are unlockable and in turn unlock the Orca in Ocean's Graveyard during the daytime.
- This area seems to be directly inspired by Yonaguni Monument, a submerged rock formation argued to be a man-made structure.