Well - there is a lot to say and tell you being so new to this. I would reccomend reading every U.W book you can get your hands on.
The majority of your pictures are using the wrong lens or photographing the wrong thing with your lenses. The 15mm and 20mm are wide angle. You need a 28 or even longer to get what you were going for. The fish and eel which are the main subjects need to be the biggest part of the picture, not the smallest. The exposures on these pics were good. The yellow grunts and the cowfish are out of focus and need a wider arperature, the water in the back is too dark. The cool sponge is too hot with the strobe and too dark in the back. Notice the last or next to last pic I think with the coral and little tunnel in the corner (it is better to submit 2 or 3 pics at a time). This is your best pic, it had good exposure and a blue water background it is well balanced. This is what you need to go for with wide angle. It needed a nice fish or a diver lifting the camera a little upward with a main sunbject and you could have put that one on your wall. The 15mm and the 20 will let you get coral and fish aiming up getting the boat, sun and divers etc. those type of pics. Overall not bad for your first few rolls out. THe nikonos system is tough with having to keep focusing the lens by distance and arperature without a screen like an SLR, so really not bad for just starting out. You will get better really, really fast by reading ,looking/studying at a lot of pics and of course practice learning to make the right adjustments on your camera. Couple of quick tips:
1. Try to shoot at an upward angle
2. Get really close to your subject, then get closer
3. Balance the strobe and ambient light to make it look like there is no flash
4. Be calm and click the shutter after an exhale to avoid camera shake.
5. Fill the frame, and see the subject and surroundings
