in blender internal the reflectivity is acessed trough the mirror value.
Set that to 0.5 and play around ith the fresnel and blend valuesvalues
I found dark blue worked better for me than black, but that depends on sky etc.
for the sky make a dome or a cylinder that covers the scene. (check blendercookies ocean tutorial Skybox, oceansim settings and compositor tricks can be used for your blender internal scene, even though this is cycles in the tutorial)
Yes, the sky background is very portant because it fills the reflection with colours.
btw in this case its called shader, not texture