I use print film as I don't care to deal with slides. I usally use Kodak gold or Fuji 100 speed film. By the way, 200 speed film with the camera set to the 100 speed setting does a fairly good job as well. If you intend to do big enlargments then switch to Kodak Royal Gold 100, it is a bit more expensive but it makes better enlargements. I tend to prefer the Fuji film for underwater pictures because it tends to give a richer color than the Kodak, the Kodak on the other hand will give you color that is closer to "real life" and so I usally use it on land, which by the way, the MX-10 does a great job on land as well. As for actually taking underwater pictures, I found that I tried to get to far away from my subjects and consiquintly (?) they were too small and dark. Don't try to take long range, wide angle views ( like landscape on land), they don't work worth a darn except in very shallow and clear water. You are familiar with the effect depth has on color, well distance has the some effect, afterall, depth is the same as distance , just in a different direction. Try to take pictures in an upward direction or at least straight ahead, down angle pictures don't work too well. Last but prob most important, tell THE PERSON ( and write it on the envelope) that these are underwater pictures and to adjust the color correction during processing to increase the red level. As you know, colors are attenuated the deeper you go and the red's are the first to go, IF the processor knows what they are doing, they can dramatically improve the look of your pictures. If you find a picture that you really like but the color is off (too green/blue)find a REAL photo lab who's name does not end in "mart" and show the print to the photo tech and tell them what you would like to see because the color correction is done in the printing process and not the developing, so as long as the neg is in focus and reasonably exposed, a good lab tech can do wonders......Next Question?