Several ocean worlds have been identified within the solar system and are targets for habitability. The dwarf planet and candidate ocean world, Eris, is located far from the sun and lacks the tidal heating experienced by the icy satellites of Jupiter and Saturn. However, the observed tidally-locked state of the dwarf planet Eris to its moon, Dysnomia indicates a dissipative past, which may be explained by an ocean sustained through its history. Here, I will discuss my work modeling the coupled thermal-orbital evolution of Eris to characterize the internal structures that can reproduce the current orbital state and to see if Eris is an ocean world and if such an ocean can be sustained to the present day. I will also explore what kind of fluid flow may be happening on the seafloors of ocean worlds, using simple models of low-temperature hydrothermal siphon systems seen on Earth as analogs.