By disabling the atmosphere, your disabling what is giving your water its true color, the sky. Instead it just gets the blackness of space, and went off that.
Basically put your atmosphere back in
A thick layer of ocean isn't deep blue really either - its deep blue because the sky is. Water being clear, only takes in the blue look from the scattering light happening in the atmosphere.
Then the color of the water you choose will show a bit better too. As whats currently happening is its going ok water = blue.... but scattering = black. And black overwhelms the blue into nonexistence.
You could try just using a oceany blue surface shader if this is going to remain from space and apply the color that way. won't technically be water, but maybe give you the look your going for?