On most live-aboard vessels, we have the luxury of a great camera area complete with power strips and other convenient amenities for setting up our underwater cameras. With these areas, usually you will find an air hose to blow the water off of your housing after a dive, hair or particles off an o-ring and other camera components such as your strobe. I see people all the time hold the hose less than an inch from their camera and blow off water. This is something most professional photographers and camera manufactures will tell you not to do. A low pressure hose is very powerful and if you are pushing air into buttons or other crevices, there is a possibility of pushing left over salt water into the areas where the buttons are or even past the o-ring. This can create big problems. If the salt water drys in those areas, you can have corrosion and other issues not conducive to underwater picture taking.
Next time you grab for the air hose, it is best to keep at least 8 inches between the hose and the housing. It may take a couple extra seconds to blow the water off, but what that will save ($$$) can be priceless.