Wow, that's fantastic. I love the glistening effects and the translucence of the manta-ray-like creature the most.
I don't think its necessary to tighten the manta ray as you said. The inconsistent outline adds to the glass-like effect. The only criticism that I would give here is that the picture's just alittle too blurry. I would like to see this with the creature as it is, but the planet just a little sharper to contrast the manta ray's ethereal appearance.
That is unbelievably beautiful. ;-;