here’s a work in progress i’ve got going on called Jellies. it’s going to be the opening animation to a larger project i’ve started that features some islands. constructive criticism please. 
This looks really good! The colors,models and textures all look great. the only thing i would suggest, would be to ad some variation to the background jellies. If they’re all exactly the same the piece loses interest. Other than that small detail, good work!
Very nice! Using the new SSS in cycles?
I agree with Democles about the variation, also the smaller strands seem a bit stiff to me. Maybe some extra detail inside the “head”? I suppose it varies from jellyfish to jellyfish, so it’s up to you, but I was thinking something like this:
Anyway, that’s all the nitpicking I can think of. Very beautiful render as it is though, can’t wait to see the animation, so don’t forget to post it. ^^,
@ Democles - thank you for the comments and criticism. right now the jellyfish are not rigged or animated, and they are being reproduced using a particle system. i’ll eventually animate one of them, then stagger the animation across them all so that they’re at various points of movement to provide that variation.
@Nimtrix - yep! using the new SSS, which looks fantastic in Cycles. the smaller strands are hair particles that haven’t been animated or variated yet. 
i’ll work on getting some more transparency in the head area. thanks for the crits!
It looks very good. The only thing that I would change would be to have more of a variation of the sizes of the jellyfish in the background. but overall it is quite good 9/10!
@justcool52 - thanks for the critique! here’s an updated image (one frame of an animation) with more variation on the jellyfish, and some water above. next up, i’m going to make some bubbles and water particles!
This looks a lot better! Cant wait for the finished project- I’d love to see how you’ve animated them.
This new image is a huge jump from the first, it’s fantastic. I’m a huge fan of Jelliess and you’ve portrayed them awesomely here! I do think that the water’s surface is a little more “cartoonish” than the Jellies but that’s about it. Can’t wait to see more!
Here’s the latest update. Lookin’ hella better. I’ve also now rigged and animated everything. Going to kick off an OpenGL animation render to see what it looks like.
Jellyfish convulse to propel themselves through the water . They would look more realistic if they were all in various stages of that movement. Also you might want to put some internal organ structures or a texture to create the look of organs .