Don, the MX-10 is perfect for beginners. You have some control over the exposures without getting into alot of really technical stuff. Just an easy, slow learning curve! The 20mm wide angle lens and the 3T macro gives you a good range of photo opportunities. As for the 8x10's, as long as you use a good quality, fine grain film, you most certainly can enlarge them. Most of the MX-10 shots on my website have been enlarged and are on the wall. Looks good to me! The fixed strobe will show up some backscatter but good news is, the newer cameras have the ability to mount to a base plate, allowing you to add a second strobe. This greatly eliminates the backscatter. Next, pond scum research expedition, I'll write and you can take the photos!
Sub, I've been taking u/w photos for about 4 years. Sounds like alot but when you consider I only get to do it on dive trips to the caribbean, that's not that long! I've been using a YS30 slave strobe with my YS50, and it's sweet! Just enough to fill in those shadows and bring out some extra details. Sorry, not going to DEMA. Sure looks like I'll miss seeing alot of folks, tho! Have fun.