1.You have to know the basics of photography- as all of them generally are applied in underwater photography but you will also need to learn some other technique and to have special materials as the light diffuses differently in the water not like in the air.
2 .You should have some diving lessons-Because is very important that you learn to stay in a stable position in the water and because most of the photography are close ups you will need to stay motionless.With diving lessons comes the diving gear that should be chosen carefully so you are safe underwater and comfortable to be capable of photographing .
3.Additional light-Is very important when shooting underwater because the colors become very muted at normal diving depths,but sometimes this is not true and you can have great photos without the beneficial of additional light,and to do these we might help with this trick:
- Shooting the above-water and underwater portions-Typically, an extremely wide-angle lens like a full-frame fishEye is used behind the widest possible dome port in an underwater housing. The air/water interface bisects the composition. Ideally, something of interest will occupy both the topside and underwater portion of the composition.You should use a Shutter Speed that prevents camera motions,let say 1/200 of a second and a low ISO,but if you will need a smaller aperture for a bigger depth of field you should increase ISO up to 200 or even 400.
5.You have to shoot close-as water sucks up lighting and flash falloff is much greater underwater.
6.Choose a place to shoot and practice a lot there-You have predetermine lighting setups,know the area so you can choose the best angle to shoot your photos and know the animals around there so you will know how to photograph them.
7.Choose the right photo gear-The biggest issue to consider, especially in point-and-shoot systems, is digital lag-that annoying little delay that occurs between the time you push the shutter button and the time the camera actually takes the picture. Even a small delay can mean the difference between a well-composed image and a shot of the tail of a fleeing fish.Newer digital compacts have greatly reduced digital lag, and with digital SLRs it’s rarely an issue.
The viewfinder of your housing can also make a big difference in terms of critical focus and precise composition.
Memory card should be with high capacity,because the more you shoot the higher is the possibility to have great pictures and you have to buy better batteries so you can shoot more
8.Capture a diver- if you want to photograph a diver.both of you have to work on your signs language and use some sounds to drive diver attention without scaring the creatures around you.
9.Always practice-Most of the time underwater photography is luck but good planning and inspired execution can make luck happen.So you have to practice and practice