Taking photos while playing on the water adds to the fun exponentially. All those great moments come back instantly whenever you see them displayed on your wall. With the quality of modern digital cameras, anyone can bring home shots worthy of a frame and display space.
Adapting to currents is one unexpected challenge. A kayaker might be able to hold onto a rock or blown-down tree for stabilization. Divers should not hang on to anything except their boat's ropes, a rocky or sandy bottom, or maybe a stable, non-barnacled part of a wreck. Leave no trace - keeping the ecosystem perfectly intact is more important than getting the shot. Besides, none of these aids will typically be available in the perfect spot for the photo you want. Therefore divers and kayakers usually have to set up a shot well beforehand and shoot while drifting by. Hopefully the current permits a few re-tries.
Although shutter lag time has improved in recent years, it is still a factor to be dealt with. This is another reason to plan for shots beforehand - be ready for the chance that the bird may start flying. Balance this preparedness with maximum battery life. When you see a shot you want to try, turn the camera on immediately. Keep it on while you line up and wait for the shot. Turn it off again while you wait for another good subject. If you can turn off the display screen this will allow your battery to last longer. Even so, always have a good spare battery available.
Many cameras have a 'burst mode' where several shots can be taken in succession when the shutter button is held down for 1-2 seconds. Pick your finger up and press again to get another burst. This is usually found in sports mode (the little running guy on the dial next to the shutter). Burst has inestimable value in capturing wildlife - if you take several shots, you're more likely to have one keeper. You might even get a series that can be framed together, such as Your Examiner's favorite: a whale breaching, then splashing, and just the tail.
Auto-focus can sometimes be difficult in sports mode. The camera may focus on the closest object instead of the one you want. Read the manual to find out how to choose the right focus point. If this feature isn't available, move the camera around and change your position while taking several shots. Enjoy not having to worry about using up all your film on bad shots and experiment all you want! A 1 gb media card is more than enough for a full day of shooting, even at high res; since the prices are so low having a spare won't break the bank. Do some online research to make sure the card has a speed compatible with your camera before buying.
Experimenting also allows you to learn all the different functions you paid for. Take the same photo in sports, landscape and portrait modes to see how they differ. Try the manual settings just for fun. Play with long exposures (waves are beautiful this way). Try to duplicate a photo you've seen in a magazine. Set the camera for maximum resolution at the beginning of the trip so the best shot can be blown up big.
Some paddlers may elect to bring an unprotected camera along in their boat. This can be successful with extreme caution. Only do it on calm, flat water with minimal wind. Have someone hold the camera while you get into/out of your boat; secure your PFD and skirt before taking it back. Carefully watch your paddle to avoid dripping on the camera as well as hitting it while stroking. Use the neck strap instead of leaving the camera loose on your lap or pocket. They do make neck straps for little point-and-shoots. Make sure the strap is short enough to keep the camera from lying in the skirt puddle. Go very slowly and use extra-vigilent, extra-diligent care in every way. There is no turning back once the camera is wet. Paranoia and obsession are totally appropriate. (Using a housing would let you enjoy yourself instead of freaking out every time a drop hits your arm.)
Divers will want to use the flash. Within a few feet of the surface, natural light is greatly decreased. The first effect is that the camera will see everything as blue. Using the flash will display all the great colors down there. If you want to shoot both in and out of the water, gently rub a piece of apple on the optical glass of the waterproof housing to get rid of water beads.
The real fun comes from enjoying your photos at home. Load them into a screensaver or digital frame and enjoy a constant parade of your own adventures. Make your own vacation postcards online. Print the once-in-a-lifetime shot as a poster if it was taken at high resolution - $20 well spent for eternal enjoyment of that perfect moment. Print more of your favorites in 5x7 size, set into simple frames and group together on a wall. Groups of photos can also be displayed on photo shelves. These thin shelves have grooves to keep photos from falling. Ansel Adams himself used them in his apartment and changed the display frequently. All sizes can be displayed together. Keeping the frames (and mats, if used) a uniform color will keep a group from looking cluttered. Using shelves also prevents the need for a plethora of nail holes everywhere.