Just about any video editor for the PC will do this for you. Microsoft Movie Maker might even. Usually you just scan ahead to the frame you want and find whatever "export" menu the program has and tell it to export just that frame as a BMP or high quality JPEG.
Don't have high hopes for the picture... it is in MPEG2 format, and so the picture is not going to be frame accurate.
Have you watched the video yet? I have always been extremely skeptical of DVD camera's ability to deal with lots of motion. I'm curious to see how it did with your dive.
Good luck!