There are several approaches to position the camera for proper cubemapping, and of course all of them claim to be the correct one.
As far as I see you need to position the camera "behind the mirror" so to say. So if you want reflective water, the env-cam should be positioned at X and Z of the main camera, but on gound - Y, eg. when the water surface Y is 10.3, and the camera is 2 meters over the surface then the env-cam Y would be 10.3 - 2.0 = 8.3 .
You can use CameraZoom to alter the size of the reflection, but a six-sided render will only cover the whole enviroment perfectly with default CameraZoom settings.
Finally, if the enviroment map is static then it will pay to make it as big as possible - if your screen isn't big enough then you can use multiple render passes. But if you plan to update the texture in realtime then I'd suggest to render as many sides as possible simultanously. Eg. rendering 6* 256^2 textures on a min resolution of 800*600 will take only one render. Simply use CameraViewport with 6 cameras. Although, 256 pixel enviroment textures are looking rather blocky.
As far as I see you need to position the camera "behind the mirror" so to say. So if you want reflective water, the env-cam should be positioned at X and Z of the main camera, but on gound - Y, eg. when the water surface Y is 10.3, and the camera is 2 meters over the surface then the env-cam Y would be 10.3 - 2.0 = 8.3 .
You can use CameraZoom to alter the size of the reflection, but a six-sided render will only cover the whole enviroment perfectly with default CameraZoom settings.
Finally, if the enviroment map is static then it will pay to make it as big as possible - if your screen isn't big enough then you can use multiple render passes. But if you plan to update the texture in realtime then I'd suggest to render as many sides as possible simultanously. Eg. rendering 6* 256^2 textures on a min resolution of 800*600 will take only one render. Simply use CameraViewport with 6 cameras. Although, 256 pixel enviroment textures are looking rather blocky.