I' m sure your already sorted for an UW setup butthought i would ad myfindings to the mix.
I took the plunge and purchased the Nex-6 and nauticam housing for a holiday to the Turks & Caicos, in August.
I went for the 16mm pancake + converters, FE & wide angle. All behind the 4" nauticam dome. I'm a novice UW photographer so kept things simple to start with.
I did look at the 10-18mm in the store but the cost was what put me off initially, although I'm now looking at it again. I would house this behind the Nauticam 7" dome which has space for the zoom gears (unlike the Zen).
I found the 16 + wide angle converter a bit more flexible than the FE, as at times I wanted to get a bit closer. When stopped down the sharpness was very good, although it does tail off towards the edges. I was pleased with the results.
All we need is a suitable macro and the package will be complete.
If you want, have a look on my Flickr page, johnquinn2011 for some of the images I took with the above combo.
Hope this helps.
Edited by Johnqdiver, 02 September 2013 - 01:18 PM.