Do I shoot Wet or dry?
A: Flat ports should always be shot dry
✓ Any drops of water on the lens element of the port will cause aberrations and soft spots in your final image.
✓ Keeping water drops off the lens element of your front port takes practice, attention to detail and more practice.
✓ Most water photographers will wax the lens element with a liquid car wax such as Turtle Wax™ before hitting the water. This helps the water to sheet right off the lens element but after a while the effectiveness of the wax diminishes. When this happens, get some body oil on your fingertips by rubbing behind your ear or at the crook of your nose. (Avoid areas that have had sunscreen applied) Hold the lens element half in and half out of the water and rub the lens element with your fingers in an up and down motion from one side to the other while agitating the water. Dunk the housing and pull it clear of the water and you'll be rewarded by seeing the water sheet right off the lens element. If not 100% effective, repeat until the water sheets off.
✓ In between sets is a good time to check your lens element and other camera settings so you are ready when the action happens.
✓ Over time, every water photographer develops their own technique that works best for them. There is no substitute for trial and error which will eventually lead to a technique that works for you.
Dome ports most often are shot "wet" but can also be shot dry
Shooting "wet" means that you want a thin film of water to cling to the dome when shooting. Surprisingly, this technique does work and produces good results even though you would think otherwise.
✓ Because of the increased surface area of a dome compared to a flat lens element, it is much harder to keep a dome completely clear of water but it can be done. Fisheye lenses typically have a very wide depth of field, so any drops of water on the dome will tend to be sharp as opposed to soft which will make those drops stand out.
✓ Almost every water photographer has a different technique for shooting wet and the most common technique is to lick the dome with your tongue. The sugars in your saliva help to create a hydrophilic surface tension that keep a thin film of water in place. Again, trial and error is your best friend as what works for one photographer may not work for the next.
✓ There is no substitute for practice and thru trial and error, you will find a technique that works for you.