After Mersad asked in the comment section about what kind of underwater housing I use I received a few more e-mails wondering the same thing.
I'll try to keep from being too technical but hopefully I will give enough information to those that are interested. Please feel free to e-mail me if you have any questions.
The last two underwater housings I have had are made by Ikelite. I like these housings because they are made from clear acrylic which allows you to see if you have any leaks, hopefully before it's too late. They also have more camera control than some of the other housings.
I've only had one leak and that wasn't because of the housing, it was the dummy using the housing who didn't put it together properly. In other words, me!
The Ikelite housing has buttons and knobs for every control on the camera. This particular housing is made for a Nikon D800. Being able to adjust anything on the camera while in the water is extremely helpful. I have to wear a scuba mask with built in bifocal lenses so I can see but that's what happens when you get old.
I also have a center mount on top of the Ikelite housing which holds a GoPro Hero 4 so that I can get underwater video at the same time I am taking photographs, The GoPro housing has a float attached to the back in the event it snaps off of the housing it will float the camera to the surface.
I have equipped the housing with two Ikelite DS-51 strobes to get more light. The first year I used one of these housings I didn't have any strobes and the photos were good but the strobes allow you to get more color even if it is fairly bright in the water which makes the photos even better.
(from the web, because he explains it better than I would)
Water absorbs different wavelengths of light to different degrees. The longest wavelengths, with the lowest energy, are absorbed first. Red is the first to be absorbed, followed by orange & yellow. The colors disappear underwater in the same order as they appear in the color spectrum. Even water at 5ft depth will have a noticeable loss of red. For this reason, strobes are usually used to add color back to subjects.
At what depth underwater does color disappear?
Red - 15ft
orange - 25ft
Yellow - 35-45ft
Green - 70-75ft
Don't forget to add in the horizontal distance. If you are 10ft underwater, and you are viewing an object 10ft away, the light has actually travelled 20ft, and all of the reds will be filtered out.
Likewise, if you light up an object with your strobes 5ft away, the light has to travel 5ft to the object, and 5ft back to your lens, for a total of 10ft, with a significant loss of reds. This is why you always need to get close to your subject.
I use an Ikelite 8 inch dome port on the housing so that I can use a fish eye lens. I used to have a 4 inch dome port which worked great except the fisheye lens sees to wide for the four inch port.
I normally shoot with a prime lens when underwater. For the most part it has always been a Nikon 24 mm f 2.8 lens. I switch to the 16mm f 2.8 fisheye lens when I want to try some split shots.
This next trip I will be going with a Nikon 20mm f 1.8 lens. I purchased this lens this year and have been extremely impressed with how sharp the lens is. I'm looking forward to seeing what it does underwater.
If your'e wondering why the wide lenses it's because in underwater photography the rule is to get as close as possible and shoot as wide as possible. A lot of that is because of the light and color drop off you get underwater. The other is because the wide lenses really make the subjects stand out.
Shooting underwater definitely has a learning curve to it (which I'm still learning) and it can definitely be hard on your bank account. The retail value of the set up I have in the photos is around $4000 and that's without the camera or lens!
I know some of the really good underwater photographers in Maui that have $20,000 in a single set up but that's how they make their living so it makes more sense.
As a hobbyest I have reached my limit on underwater gear, at least that's what my wife tells me! LOL
An underwater housing can be used on top of the water too. It keeps you from worrying about that nasty sea water ruining your camera.
Normally a shot like this would be taken from a plane or helicopter but in this instance I was standing on the top of a volcano at 10,000 feet. You can just barely make out the ocean and part of the island of Maui in the bottom of the photo.
The sunrises on Haleakala volcano are supposed to be spectacular but I don't really want to get up at 2:00 a.m. to make the trip to the top of the volcano so I opted for a sunset instead.