Message in a Bottle

I like the idea, but the execution is lacking a bit.

There's a white line around the bottle where you haven't fully erased the background of that image, which really quite spoils it.
I like how you've tried to make the sea visible through the neck of the bottle, but I don't think simply erasing the bottle was the right was to do it. It just doesn't look like you're looking through glass. I think it would probably have been better to play around with layers and transparency, so that you still had the element of glass, but could see the water through it.
Also, the base of the bottle doesn't interact with the water at all. I can appreciate how difficult it would be to make it interact, and I like that you've tried to place it somewhere that it doesn't cause too many problems, but something doesn't look quite right.

I know I've written an essay - sorry - but these are fairly minor things that should be quite easy to fix. With a bit of practice, I think you could create some really nice images.