FiKAIeldJOU

fiKAIeldJOU (called on the JASRAC database) is Disc 3, Track 7 on the XenobladeX Original Soundtrack. It is split into two parts: the first plays from the start until 3:11, and the second plays from then until the end.

The first part plays in the oceans during the day: NLA Waters, Primordia Waters, Noctilum Waters, Oblivia Waters, Sylvalum Waters, and Cauldros Waters. The second part is a (slightly) more subdued remix of the first and plays in these areas at night.

Etymology
Separating out the lowercase letters from the uppercase in the title gives 'field' and 'KAIJOU'. The latter can be translated from Japanese as 'of the sea'. This also aligns with the JASRAC version of the title.