Latest updates on the osgOcean trunk fix some known problems in UWSim and bring new cool features. The most interesting one is the support for light refraction effects and underwater light scattering. Until now, the sea surface was completely opaque. Now it is possible to see through the water surface, being the image distorted due to the light refraction. Other fixes include a better rendering transition between the surface and underwater, or the possibility to choose between different pre-defined sky textures and lighting conditions (which was broken in previous commits of UWSim). You may want to try the new keybindings: 'R' enables/disables refraction, 'r' enables/disables reflections, 'T' enables/disables scattering, and '1', '2', '3' sets the different pre-defined light conditions. See below two short examples of refractions, corresponding to the cirs.xml and shipwreck.xml scenes.