I really like this. I like the imagery of salt water stinging the speaker's lungs; it's a really nice visual and metaphor. I also like the way you wrote that last line. I can relate to how the speaker may be feeling because I actually got a little dizzy, as I was reading it. Was that intended? If so, nice job.

Nice! Keep up the good work, Z!

Sometimes breathing is
difficult when my lungs

^
Personally, I would leave "difficult" on the first sentence of the stanza.

I like the comparison of the salt water and the frantic thoughts that are running through the mind.

over all I think it was a good poem.