It's the start to a video about Morrowind made by the guys that did http://www.gamesas.com/topic/1351887-dunmer-cullture-striders-hd-video/. Made in 3ds Max and Adobe AfterEffects. Not sure who stole it and pretended it was Bethesda's.
Thanks for clarifying that, Lady Nerevar. Hmm... too bad it had nothing to do with a mod, but there are some great mods out there for MW, anyway that could achieve a similar effect (like MGE, abot's boat/silt strider travel mods, various retextures and expansion mods).
I watched the Silt Striders video, and it was entertaining, though weird. I'd love to see the whole video of Vivec.