Here's a code example of cubemapping for water reflections, the sky is a skysphere not a skybox, skyboxes are better because there is no visible distortion.
Simple Cubemapped Water (with skysphere)
http://www.blitzbasic.com/codearcs/codearcs.php?code=1788
Simple Cubemapped Water (with skysphere)
http://www.blitzbasic.com/codearcs/codearcs.php?code=1788