One of the biggest disappointments of the Sony HDR-AZ1 is the fact that there is no flat lens mount or flat lens underwater housing. With the current SPK-AZ1 it is all but unusable underwater since the curved lens results in out of focus video despite the high quality of the Zeiss lens. This adapter helps correct that.
What you need for this is two additional items. the first is some 3M waterproof double-sided tape or equivalent, something like 3M VHB 4926 which is available in discs from places like Digikey. A cheap 40 mm video camera glass UV filter from eBay. You must make certain that the glass can be removed from the metal housing.
Carefully press the front lens of the SPK-AZ1 from the inside toward the outside to break the seal of the existing adhesive. You can press fairly hard since it is a glass lens. Once the convex lens is removed, clean off all the remaining tape residue from the face of the housing. place a circle of the 3M tape where the existing tape used to be. Remove the upper protective layer from the tape and press the modifier (this piece you are looking at right now) in firmly. Place another circle of tape in the top edge of the modifier and set it aside. Take you UV filter and unscrew the housing parts to remove the actual optical glass. Make sure it is cleaned on all sides. Go back to the housing and remove the backing from the tape and firmly press in the UV glass filter. Set the whole unit aside to allow the adhesive to set.
Alternative attachment method
Using an adhesive like UV Curable LOCA glue will also work (Bondic or equivalent). The UV filter does not block 100% UV rays, so a small amount of extra time under the UV LED will still cure the glue. Note, this is the same glue used to attach glass to smartphone LCD panels and is optically clear when set.
Do not submerse the housing for at least 24 hours. Doing this modification will void the warranty on the housing. The Sony AZ1 housing is only rated for a depth of 5m/16ft and this modification does not extend that limitation. While every effort has been made to make sure this modification works, there is no guarantee of success. Do this at your own risk.