IMHO..normally in underwater, we do not see shadow as such unless its very shallow and the sunlight are very harsh and the water crystal clear. If there is shadow, its normally very very transluscent (sp?) With regards to your figure, I find that the point where the tail bend is a bit on the 'steep' side. May be its the angle of view, but it be great if you can have a more 'blending' curve that suggest a wavy movement of the overall body structure.