Welcome to YWS! Hope you're enjoying the site so far Here's my take on your poem - keep in mind that this is just my opinion, but I'd like to help you improve it if I can
First off, rhythm and rhyming. You've used rhyming here, and in general it is well done, and fairly natural. Interesting rhyme scheme too. However, I think it would work better if your line breaks were more even and you had a bit more punctuation -- a bit more rhythm, I guess is what I'm saying. Try reading it out loud and tapping out the syllables on your desk or with your foot. If you're musical, this will be easy. Basically, the trick is to find a kind of internal pattern with your line length/rhymes etc. that is smooth/flowing and (if you're lucky or really clever) helps to add to the meaning of the poem. So, for example, in this instance you're talking about the sea, so you could base your rhythm on the tide, the sound of waves (in, out, in, out, that type of thing). Just remember that rhythm can be a tool too, and the more you use it, the better your poems will be.
Second: the story itself. Or in this case I guess I should say the subject? Whatever. It's intriguing, definitely. I'm not quite sure what you're trying to say, though. Who is the poet? Why are they under the water? Is this simply about someone drowning or is there more to it than that? Perhaps a bit more expansion on the background/context would enable the reader to understand the poem a bit more. Even if it's simply about someone dying, we at least want to understand that person, how they feel, what they think, the exact sensations as the water presses in on them and rushes into their lungs....**shudders** At this point, what I'm reading is a pretty clinical and disinterested account of someone sinking. I dont get the impression that s/he is afraid, I dont find myself imagining what they must be going through...in short, I am disconnected from the poet. Try for a bit more emotion, a bit more imagery and imagination. I bet it will make the poem heaps more powerful!
NITPICKS:
Turquoise blue water surrounds my body, Bubbles of sweet air escape my mouth, The sea sings to me its wet melody, But it was my destiny.
No reason for "but" in that last line. The last line is too short and messes up the flow; you repeat the same sentence structure too much. Try to differ a bit. Also, no need for a capital at the beginning of every line. Throughout the poem you switch from present (it is) to past (it was) tense. This is confusing - try to stick to one or the other! I'd suggest present tense to make it more immediate and dramatic, but it's up to you.
Tons of water beat down upon my head, I close my eyes and pray to God for help, Suffocating in blue, I begin to sink like lead, I was as good as dead.
You repeat the same pattern as the above verse, and you're not telling me anything new. Perhaps make this more about the prayer and less about suffocation/death? You've got enough of that in stanza 1.
From under my eyelids, I see worlds flash by, I am disoriented in the ocean's roll, Confronted by a thought I can not deny, It was my time to die.
Dull. Sorry, but it is. The idea of "worlds flashing by" is cliche and tells me nothing new, again. Try something original. Also, instead of just breaking your poem up into four arbitrary lines per stanza, I would advise organizing them into stanzas based on ideas instead. Like, in one stanza discuss the images and sensations the poet experiences as s/he descends through the water; in another, the feelings and emotions, and in another, her thoughts etc. Of course, you dont have to group them together like that, but this poem is largely repetitive and using stanza breaks to divide into new concepts or to progress the story would help eliminate some of the dross.
And there I lie still today on the sea's floor, Embalmed by crustaceans and ocean weeds, I had seen the light and had reached the door, I have left this world forevermore.
My reaction here is "Ummm....so?" The problem is that:
1. I do not empathize with the narrator.
2. I dont really understand what's going on.
You clearly have a vivid imagination and there is a story here that you want to tell. My advice to you with this would be to expand it, go deeper and explore the idea. Right now, you're sticking with surface stuff (pardon the pun), talking about how s/he is going down yadda yadda. What you need to do is perhaps use some more imagery (I like "embalmed by crustaceans" -- some more of this kind of thing would be excellent) and work on getting your readers to put themselves inside the narrator's head. Why is s/he down there? Why doesnt s/he fight? Why does s/he calmly accept it as "destiny"?
Think about your message. Do you want to explore the sensations of drowning in realistic (or quasi-realistic) detail? Or do you want to explore the more metaphorical sensations of surrender,allowing oneself to be swept away by the tide, or being crushed by one's emotions? What do these things make you think of? How does the water feel? What does it represent?
Dig deeper into your story and I'm sure you'll come up with something awesome.
Thanks heaps, Bubbles.
You certainly put a lot of effort into that crit, and you pointed out some really awesome stuff. I'll get digging I am having trouble with rhythm and originality, as you mentioned, so I have to work that problem out...
And I have a crazy imagination, it's just wild. You've been a great encouragement, thanks.
Wildlove100%
Here's my take on your poem - keep in mind that this is just my opinion, but I'd like to help you improve it if I can 
