Jack recommended the relatively small Nauticam Wet Mount WA Lens. I like the looks of it. I'm not a great fan of spending a ton of money on the Inon wide angle plus dome setups, mainly because you depart so far from the compact camera ethos. I prefer something that is more compact that does a modest wide angle enhancement, and does not cost more than the price of the camera and housing.
The challenge now is that camera lenses have gotten wider. Just a few years ago, 35mm was typical for Point and Shoots, and many of the wet lenses were designed to match that. When 28mm became more common; the older lenses were found to vignette and new versions were released, like the INON 28 series. The LX5 has a 24 mm lens, and the difference is quite dramatic. But -- the LX5 will vignette with almost all the older 28mm wet lenses. So we're a victim of progress, in a good way. The trick is to test any wide lens, because what worked before might not now.
For instance, look at the visual review of wide wet lenses for the Olympus xz-1 (with 28mm lens) done by Reef Photo here in June:
http://www.scubaboard.com/forums/olympus-outlet/386884-xz-1-pt-050-wide-angle-lenses.html
That gave you a pretty good idea of how the various available lenses worked with the 28mm XZ-1. Enter the LX5, wider at 24mm. Many of the lenses shown in Reef's review will begin to vignette with the 24mm. A few lens makers rose to the challenge.
I have not found a round-up review of WA wet lenses for the LX-5, but piecing together what people say, it appears that there are a few options that are good optically, don't vignette, are compact and inexpensive. (I'm ignoring the ultra wide domes, because they just don't make sense to me, but that's personal, they may for others. I do note that they were designed for 28mm and will probably vignette on the 24mm lens of the LX5.)
One candidate that Jack mentioned is the Nauticam wet WA lens, maybe a .7x magnification, small, good optical performance, reasonable price ($240).
Nauticam Wet Mount Wide Angle lens - Compact Camera Accessories - Compact Camera Systems - Nauticam Housings & Accessories - Optical Ocean Sales Underwater Photo - 800-359-1295!
Another candidate is the new Dyron DY.UAL67 II. It seems to be a .5x magnification lens that has good optical performance, does not vignette with the LX5 and has a higher price ($400) and larger size.
Dyron 14mm Wide-angle Lens with Dome (DY.UAL67II) | Bluewater Photo & Video
I won't pretend this is a complete list. I just mention the two lenses I know of that work will with the LX5.
.
