Update: the Facebook posts is now removed.
Nikon does not have an underwater camera in their current product offering. The pictured package is quite big for just a point and shoot camera, but it may contain more than just a camera. The Coolpix lineup will be refreshed in August (Nikon point and shoot announcement are always in February and August) and there will be another major product announcement at the end of August. It will make sense for Nikon to introduce a new underwater camera, but something tells me that it won't be more than a point & shoot model.
Just two days ago I reported that the Nikonos trademark already expired back in 2008.