Thalassa

In Greek mythology, Thalassa ("sea") was a primordial sea goddess.
Thalassa is a moon of the planet Neptune.
Thalassa is a fictional planet, a waterworld in Arthur C. Clarke's novel Songs of Distant Earth.
In biology, Thalassa is a genus of ladybird beetle.
Thalassa is the title of a late poem written by Irish Poet Louis MacNeice.
Thalassa is a band which represented Greece at the Eurovision Song Contest 1998.
Thalassa is the name of an electoral ward in the City of Onkaparinga.

Panthalassa ("all seas") was the global ocean surrounding the supercontinent Pangea.
Thalassa is a French TV documentary