The best option is the Inon UFL-G140 SD Underwater Semi-fisheye Conversion Lens, which corrects the underwater view from from 94° to 140°. It's a water contact lens, so you can't really use for half-half pictures (as your example above). There is a workaround to apply a special O-ring (and contact the lens underwater.
There is a new cheaper alternative, the AOI UWL-03 Wide Angle Lens (almost half price) that has a similar quality.