Revised:

I stand upon the stony shore and watch the waves; their white tips whipped to a fine spray by the northern wind that tears at my sodden clothes. I wipe a lock of hair from my eyes.
Sometimes I dream I skim inches above the waves and, with my tongue, I taste their foam. The salt stirs memories of vast shadows that twist and sing beneath the waves as they hunt. In my dream, the weight of remembrance consumes me--pulls at me--and I plunge, spear-like, into the waves to join the chase.
Though I dream these things, it doesn't make them less true, or less real. Already, I feel the sting as bloody feathers rupture though my skin and unfurl in the biting wind. Already, the stones at my feet swell into boulders as I watch and I feel...light...as a bird. The splash from a wave rinses the blood

"It is full of memories; of vast shadows..."

I struggled a bit, finally deciding that 'it' really does refer to the foam. Nit: the semicolon should probably be a comma.

"... that twist and sing beneath the waves as they hunt."

Similarly, I struggled to decide what 'they' refers to; didn't come up with a candidate.

Nit: I skim inches above the waves['] tips

The last couple of sentences were probably really happening, but the events were so fantastic they felt like part of the dream. Maybe this is just me not getting it.

There were several echoes. You are very intentional with your writing so you may mean every word in place, but if not, I thought I'd mention it.
The word -waves- was used quite a bit, and the word -already- stuck out.
I know it's an ocean bit, and there are waves, it was just something I noticed.

Already was meant to echo. I liked it, but it is a matter of opinion as to whether it works as I intended.

Not all echos are bad. When I post a piece on Hatrack I never mention all the things I think may be wrong with it. It would prejudice people to consider something they may otherwise read past.

1) "Already, I feel the sting as bloody feathers rupture though my skin and unfurl in the biting wind."

IMHO, change to:

"The sting of bloody feathers rupture through my skin and unfurl in the biting wind."

2) "I wipe a lock of hair from my eyes."

IMHO, change to:

"The wind pushes a lock of hair from my eyes."

The hard part about first POV is deciding when the "I" word is necessary. I think your opening line "I stand upon the stony..." is important because it places the narrator in the scene. After that you have to decide if its necessary to have the action happen through the narrator or just to describe it.

I have a lot of respect for your work, and about 99% of the time I won't comment just because I feel its great enough to stand alone, but I will say something this time, and this comes from a person trained to read Shakespeare - It's very interesting prose, but it took me several times going back over it to understand it, and I'm not sure that's a good thing, because though I enjoy Shakespeare and the challenge of understanding the many interpretation you can get out of one paragraph, it's great to speak, but very hard to enjoy reading. It feels very poetic, as if it has multiple interpretations so each individual line could be spoken as separate entities, so they never really tie together like normal prose, but I'm just letting you know, and I think this is the first time having read other 13's of yours that if the rest of the story continues at this depth for each sentence it would be very hard to absorb. You are a great writer, It did hook me, but also lost me.

Just my 2cents,

W.

I haven't written anything beyond what you see...it was really just a quick bit of fun. I know where it will go, but I am just experimenting with it at the moment.

A little poetic prose does hook--unusual word usage and constructions--however I agree...you would need to level out 0n an easier-to-read path fairly quickly or the reader would tire.