A pretty clean render mate but I miss the professional quality of the light, or lack of here. It doesn't truly show it's all submerged in any way, no shimmer or reflective things/bubbles/surface thingys or alike. I think you need a better atmosphere with the light here and not perfect visibility in terms of getting a better aqua feeling to it.
A process required by a computer to generate an effect, transition or composite.
E.G. You make a bunch objects in 3D, you put them where you want in the scene, you tell the computer what materials they should and what those materials properties should be, place some lights in the scene and set their brightness and colours etc. At the end of this process you are usually seeing a type low-res version of the final scene (see the first frame), when everything is set up to your liking you would hit a button usually called 'Render', and the computer will then calculated all those light, material and colour interactions yo produce the final somewhat, one will often hit the render button many times along the way to 'test' or preview the scene as it is being built up.