She did say she and uncle Poseidon(or was it Neptune?) were pretty close.
Note: Poseidon and Neptune are the same god, one of the 12 Olympians of Greco-Roman myth. Poseidôn (Ποσειδῶν) is his Greek name, while Neptune is an anglicization of his Latin name, Neptūnus.
Lore-wise, Gura would be more likely to know him by his Greek name. Atlantis was held by Plato (in Timaeus, ca. 360 BCE) to have been part of the Greek-speaking world in times more ancient than his own.