UWL-04 0.42 x Ultra-wide Conversion Lens. Includes 52mm to 67mm adapter and neoprene cover. Gives us to 165 degree angle of view (diagonally) .
This is the widest 'wet' conversion lens we know of that's available for a compact camera housing. This extreme wide angle view is brilliant for shooting really large subjects including wrecks, dolphins, mantas and other divers. It'll allow you to get really close to your subjects whilst still fitting them within the frame. By being so much closer you'll get hugely clearer and more colourful pictures. Or if you are lucky enough to be swimming with a pod a dolphins that get close to you you'll be far more likely to get them all in the shot rather than cutting off their heads and tails. The lens doesn't produce super sharp results on the edges of the shot, which is to be expected when working with a really wide conversion lens, however the increase in quality you gain by reducing the amount of water between you and your subject more than makes up for this.
This lens can also allow you to get brilliant pictures of smaller subjects such as lionfish, however you will have to be exteamly close to make smaller subjects fill the frame. This makes these kind of shots challenging to take. For general purpose reef photography where you are not expecting really big subjects, a slightly less wide, wide angle lens might make more sense, such as the Fantasea UWL-400F which shoots at 120 degrees.