First idea... you could maybe name them after the Greek titans: Hyperion ( titan of the sun, male), Oceanus ( titan of all the rivers and oceans , male), Leto (titan of mother hood, female) and Selene (titan of the moon, female) ot you could use Tethys ( wife of Oceanus,titan of Brooks and rivers)

Or you could go with greek myth figures by theme :
Sea monsters& witches
Scylla (sea monster), Charybdis ( whirlpool sea monster) , Circe and Calypso

Greek god couples : hades & Persephone, Dionysus & ariadne or zeus & hera or poseiden & Amphitrite

Love odd names and Greek mythology!