Are you/can you white balance underwater? That purpleish hue to the water at about 1:00 on the Helma Hooker clip is pretty distinctive of a red filter without white balancing. If you can, you should be white balancing with any significant depth changes - more often in shallow water, less often in deeper water. Also your shots need to be slower and more stable- which is the problem with about 99% of people that shoot underwater.
As far as classes, if you can't find someone that has something pre-packaged, find your favorite videographer and ask them how much it would cost to do a video course. I have asked a few great cave photographers (Becky Kagan-Schott and Jill Heinerth for example) about doing a cave photo class and all were more than happy to schedule one for a reasonable day-rate. I haven't had a chance to follow up with anyone for an actual class, but it is just a matter of making it a priority on my part.
-Chris
Excellent tips and course ideas! I'll most certainly work on them and will start reaching out to videographers as well! (that was a great idea trully)