m-mef, you should post these questions in the wetpixel forum. The people there are hugely experienced and you'll get better answers. This forum here is good for general travel questions, but for the kind of specific advice you need, go to a specialist forum.
Are you talking about wetmount lenses for the p&s housing? If so, those require a flooded lens in order to work, and the ones for your DSLR most likely require air surrounding them to work. But don't go by just that... ask in wetpixel instead. :-)
