I have tested and used this for some time
http://www.ebay.com/itm/XPRO-F500-67mm-Close-Up-Lens-Macro-lens-Super-Macro-Conversion-Lens-/280874520769?pt=Camera_Filters&hash=item41656d10c1
mostly using the 49mm on my Nex camera lenses.
Images:
http://images5.fotop.net/albums7/herbridge/Sipadan_2013/DSC2238.jpg
I wonder if this can be used underwater