The Olympus PTMC-01 is a high quality macro conversion lens that works on many of the Olympus housings that have a 67mm thread. It attaches to the front exterior of the housing's lens port. The lens could be used with other Olympus housings with the use of a step-up ring. It has a magnification of 2x.
The PTMC-01 allows you to get close to small subjects. This will improve your underwater photos by increasing contrast and color saturation.