A few with possible water connections…
[name_f]Cyane[/name_f]: a naiad, related to ‘cyan’ - the greenish-blue color.
Ilayda: Turkish name, supposedly that of a water sprite?
[name_f]Melusine[/name_f] or Melusina: a type of water-spirit in European legend. The Starbucks logo is based on a melusine.
[name_f]Nimue[/name_f], Niniane or Nyneve: names of the Lady of the [name_u]Lake[/name_u] in Arthurian romances.
[name_f]Odessa[/name_f] or Ottessa: the city of [name_f]Odessa[/name_f] is known as ‘the pearl of the [name_m]Black[/name_m] Sea’. A similar name is Ottessa, borne by novelist Ottessa Moshfegh (don’t know its origin but find it intriguing).
Thalassia: epithet of [name_f]Aphrodite[/name_f], derived from Greek thalassios ‘of the sea’. Thalassia (fl. late 2nd century BCE) was a queen of Characene, a small kingdom in what is now southern Iraq. There’s also the simpler [name_f]Thalassa[/name_f], a primeval goddess of the sea.
[name_f]Yara[/name_f]: a water-spirit in Brazilian legend.
ETA: @namergirl3 haha my boyfriend is playing that too! Her name has grown on me 