I proposed underwater, in a Florida cavern. I had two diveshops and a number of other divers volunteer to film it for free. The thing that was disappointing about it was that an underwater proposal was actually a very short event. Probably 15-30 seconds of actual "proposing". The rest of your video is just a dive video. Great to have, but not particularly relevant to the proposal. It's almost an "oh yeah, and we also saw some fish on that day."
If you actually want to ask and get a response, consider renting or buying full facemasks with comms. I did, and it was well worth it. A shop in my area charged $100/day for two masks with comms on each. I wish I had a third radio so I could have dubbed the audio onto the video. The shop I rented from gave us a demo in their pool. They're not difficult to use, but do warrant a few minutes of instruction time.
In my case, it was a surprise. It took a decent amount of work to plan and execute without her finding out in advance. I'm sure she knew what was up when a team of people followed us into the cavern...
I always ask for raws or unedited video when hiring a photographer or videographer. Maybe they will produce a great edited result, maybe not. This is especially risky with old school film photographers. Not because of a lack of skill, but a lot of them tend to hand you low resolution images/video often with ghastly watermarks. Later if you want to get something blown up for your wall, use it as a desktop wallpaper or just about anything else it will look awful. If I can get edited+raw, then so much the better. However for me, no raws = no sale.
I agree. I had a "stunt" ring made. It was under $200 extra from the jewler who made the real ring, and I couldn't tell the difference - he had to mark the fake for me. Also, I still tied it off to myself with a string.