Autofocus...please advise.

I ordered a canon hg20...but I am second guessing myself because the manual focus is really hard to use unless your in ideal conditions (on land/ tripod). I have seen videos of a HF100 under water (same camera / lense / functions...just lacks the 60gb hard drive) and it does great using auto focus. I asked the guy who took the videos, he said the autofocus behaves for him. I just don't know how critical it is going to be.

this is a link to those videos

http://vimeo.com/2686762

I don't see the camcorder hunting for images, and it looks pretty good (considering he doesn't white balance or have external lights)

This is my first camcorder setup ever, underwater or not. I just want to film decent videos that I can be happy with...am I over thinking this? Can anybody offer any alternatives to this camcorder for 600-700 dollars?

For filming WA stuff, just zoom in a little and focus on your fin. Lock the focus to manual and then zoom out. Everything from about 40cm and out should be in focus. Some cams vary a little and you may need to tweak but that will stop the hunting and make it easy to focus. Macro is different and you will have to adjust especially if you are zoomed in and the DOF may be a lot smaller