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In this work we study the transport of methane in the external water envelopes surround-ing water-rich super-Earths. We investigate the influence of methane on the thermodynamics and mechanics of the water mantle. We find that including methane in the water matrix introduces a new phase (filled ice) resulting in hotter planetary interiors. This effect renders the super-ionic and reticulating phases accessible to the lower ice mantle of relatively low mass planets ( ∼ 5 ME) lacking a H/He atmosphere. We model the thermal and structural profile of the planetary crust and discuss five possible crustal regimes, which depend on the surface temperature and heat flux. We demonstrate the planetary crust can be conductive throughout or partly confined to the dissociation curve of methane clathrate hydrate. The formation of methane clathrate in the subsurface is shown to inhibit the formation of a sub-terranean ocean. This effect results in increased stresses on the lithosphere making modes of ice plate tectonics possible. The dynamic character of the tectonic plates is analysed and the ability of this tectonic mode to cool the planet estimated. The icy tectonic plates are found to be faster than those on a silicate super-Earth. A mid-layer of low viscosity is found to exist between the lithosphere and lower mantle. Its existence results in a large ar X i