Refraction is good
.. also remember, when you look through liquid things magnify.. put a straw in a glass, stand back and see if it alters at all... keep that on your desk and then change the tube going to the bottom to be that much bigger or w/e.
On the next render, dont give it a wall (the dark edge).. keep the exact same thing oyu have, with that awesome blue gradient.. and then put a "background" shader on a plane and render out its shadow, like you did in the above. If you do this i think it will just bring your attention that much more to the bottle.
Add some thickness to the green cap, just grab all the edges on the bottom and extrude inwards.. keep in mind i work in maya.. so some of the things i say may be different to do in LW.
Other than that.. wonderful job!
If you want me to keep looking at it and seeing if i can spot little things.. let me know
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By the way, i have this weird suspicion that you made your refrence after you modelled the bottle.. because that cap that you modelled for the bottle is really lacking in your refrence, just looks like a outline of where the model would be.. hahaha.