Pekka,
i photograph while freediving. i just recently got into a new setup but i've gotten quite a few good shots with just a point and shoot.
this
post might help you a bit, or at least get an idea of experience of the people who helped me out.
to start, you have to remember that water in any sense is just a big ol' filter. the more distance you have between you and your subject, the darker the subject will appear and the darkness will increase as you get deeper(away from the sunlight).
there are so many factors in uw photography, you should think about picking up a few books on the subject. i've picked the brains of several professionals, including Cliff Etzel here on Deeper Blue. i'm sure he'll drop in for some advice for you as well.
next time you're in the water, you should try some different things while shooting. experiment with getting as close to your subject as possible, and that's if they don't mind
. when you get your pictures developed, you'll see a tremendous difference in color, even without using a flash, with the closeups as opposed to the distance shots. also keep in mind the amount of ambient light that's reaching your subject.
but again, there are so many different factors in photography. i think it all depends on what you are trying to acheive. everyone has their own style. i guess if you were to choose a published photo and say "hey, i like that. i want my pictures to look like that", then we'd be able to tell you exactly what you need or how to go about getting as close to it as possible with your setup.
later,
anderson
ps. also, there are a few ways to bring color into your shots. you can either start with the processing(kodak is promoting uw photo development) or you can adjust colors in your scanned pictures through photo-editing software. i use photoshop.