While as of this moment the D3s has been on the market for over a year with no housing, I know that at least one housing (Aquatica) is coming soon. This is an amazing camera.
Besides underwater photography use, the high ISO capabilities make it great for night time photography, and the fast 9fps for high speed shooting comes in handy. I keep my D3x in the housing and the D3s on land most of the time. The video is 720 vs 1080, but that's okj, it's all most of us need and is great quality.