I cannot recall the specific oring now, but the information is readily available on Reef Photo's web site. The Nauticam port orings are much thicker. I would not even consider using one. E_Viking may have solved this problem. if you turn it fully counter clockwise, it locks again. Backing off just a little frees it up. I was not quite sure what he meant, but stopped in Ocean Optical, and Jack Connick showed me in Person. Many Thanks.
The 10-17mm is too wide for sharks, but a wonderful lens. My shark lens is a 17-55 Nikonf2.8. You might get by with a 1.4 tele-extender for the 10-17. I have the 100mm Zen minidome. It is made for the Tokina 10-17, and works great with it, but probably will not work well with other lenses. For macro, you will need something like 60mm, and a flat port.