This is a good depiction of what it is like while suffering problems of low self esteem whether it is because of family problems, bullying at school, just not having very many friends, or anything else that could cause such a let down in someone and make them not feel good enough. Short and bittersweet, this gives an outlook of how one may drown when their dreams seem reachable yet are so very far away. I have personally been in this state of drowning in the anxiety of everything seemingly crashing down on me, and sweet dreams being only lies.
I think this has really a really good flow in this peace, and the rhythm and wordplay work very well together. However I think it needs a little consistency. In the beginning the reference to saltwater has a powerful hook, but it would seem a little more developed if that motif was repeated more throughout the poem. I think the emotional part is perfect, and I usually like my own poems to be just as vague about the back story. However conventionally you could add more, though it is not necessary for a finished feeling to the piece. Altogether this has so much great potential.
Excellent piece, makes one think of Edgar Allen Poe's work, as one of the other commenters pointed out. Very deep, very passionate, very powerful. Well written, and expressive description really finishes off the point. Well done.