Thanks for your input Marty,
I ended up ordering an extra one from Blurfix because as you say, 10 bucks includes free shipping.
I do have a question though, do you tend to use your Blurfix outside of the water? I was doing some test runs with it and it seems like in bright scenarios, there are some wicked interior reflections of the dome lens onto the back side of the filter. This is while testing it in pretty bright sunlight (as I'm sure on a boat, pre-dive would be).

Here's an example (extreme close up, whoa!

)
My scenario concern is this: Predive, on the dive boat, I'm interested in shooting some footage above water of my wife and I staging our gear. I would prefer to setup my camera on land prior to heading out onto the boat for the dive, but, if the reflection is that bad, it seems like the footage might not be worth it...
Has anyone had any issue with interior reflections?
I know it sounds like I'm pretty negative about the Blurfix, the fact is, I'm super happy with it! My underwater tests (sink so far) are great, and I'm looking forward to using a circular polarizing filter on it to do some time lapse footage of the sunsets over the ocean. The installation was simple and the kit feels very professional, I'm purely raising these questions so I can get some great footage of our trip (and I have minimal time to practice before the trip, but enough time to purchase odds and ends if people have better accessories for it). So I appreciate all the feedback (and of course, all of Marty's videos as those are what convinced me the Blurfix was the best solution out there).
Chris