Once the camera is charged and the SD/SDHC card is in place it is important to make sure that the seal is closed and has clicked and locked in place. This is where the camera needs to be water tight. Water in this area would damage the camera, battery and memory card.
I was using my Vivitar 950WHD in the Red sea. The salt content is extremely strong but the camera preformed well. It is important to point out that when using any camera in salt water it should be rinsed well after use. I did this by using the showers on the boat and beach then left the camera upside down to dry well, following the cameras instructions. Also never open the battery/SD card cover until completely dried. Doing so will damage your camera/camcorder.
Only downside I found to using this camera underwater with the sun shining brightly above me was not been able to see the screen well, but I still managed to capture all I needed to.