MX-10 macro, the camera really does a nice job with macro lens and the strobe.
First...get your buoyancy control DEAD ON. With macro photography, your diving skills need to be at their peak, average skills are not good enough. You need to be able to hover with very little movement and be able to back out of spots. I would suggest you find a pool and practice before grabbing the camera. Here is a practice drill for you.
Try hovering off the bottom with your feet up somewhat, your head down and your arms extended. Place your hands together to form a tube, your fingers touching each other except for the little fingers, thumbs and index fingers closest to you and your little fingers fartherest away - that is your macro "framer". Now swim up to an object, get it IN your "finger framer". A suspended ping pong ball is a good choice. The object must not touch any finger but it must be inside the "tube" they form. A macro framer only has a depth of field of 3 to 5 inches, about the same depth as your hands. Hold the composition for a few seconds while you take your imaginary shot. Now back out a couple of feet . When you can do this easily, grab the camera and try it again.....it's a lot more difficult than it sounds but IMO that is where your dive skills need to be before tackling macro. You don't want to crash into anything with your framer but still if your outside of the lenses depth of field the shots will be out of focus.
The macro lens must be installed under water, making sure all the air is out from between the 2 lenses, otherwise you will get air bubbles in the frame. I just removed and replaced it after getting by buoyancy adjusted. The camera is set to F-22 or F-16 depending on the subject, I found F22 worked in most cases. The macro lens and strobe are adjusted for 100 sp film, 400 will not work well, most all of your shots will be overexposed if you use 400. The strobe needs to have the diffuser installed. If you are using the YS-40A it can be in "ON" or "auto".
The uprights on the lens are the framer for the shot. Your subject must be within the "U" formed by the 3 legs and a distance of no more than 2 inches of the framer at F-22 and 1 inch at F-16 to be in focus. The framer legs are the sweet spot for focus, the closer your subject is to the framer the better. Your total depth of field (focus zone if you will) is only 3 to 5 inches wide with the framer being the center of the field. Now you see why control is so important.
For subjects, things that don't move are my choice for a beginner. Shells, tube worms, corals and nudabranches are some good choices. Fish are a lot harder to coax into the framer and even the tube worms are hard to ease up on.
So, practice without the camera, practice with it in a pool (no need to take a lot of photos-just framing and holding the shot will do- better yet take the "photos" with no film...might as well practice shutter control ) and then find some easy subjects to start on. It's really pretty easy to take good photos with the MX-10 and macro lens IF you are a good enough diver to hold the shot.