Probably just some random floaters, but due to the fact that she has them at such a young age, it's just a good idea to have someone check them out, preferably an opthalmologist, and sooner rather than later (i.e. today or tomorrow). Especially if she is extremely myopic, or has hit her head recently. Take note of how her symptoms change, and whether she sees anything like a black curtain over part of her vision, flashes of light, or sparks. Ask the doctor whether he/she feels that she needs a retinal exam.
Again, she is almost certainly fine, but you should always be particularly cautious with unusual eye problems. Waiting to see if the problem goes away could lead to other problems.
Actually, re-reading your message re: "black ocean on the bottom of her eyes," - what i said in my previous message still stands, but this phrase makes me even more concerned about the urgency of the matter. This could be like the "black curtain" notion I mentioned earlier.
I had a detached retina when i was 23, and what I saw at the bottom of my eye was like a black curtain.
Hopefully, it is just floaters, but you have nothing to lose by going to an opthalmologist to have her eyes checked. If you tell them about what your daughter is seeing, they should be able to see her on an expedited basis.
I'm sorry if this makes you worry, and it is probably going to be nothing, but you'll feel better if you take her in now. If she does have a detached retina, you have an extremely limited window of opportunity to address the problem.
Hope it goes well, and i am likely wrong. Sorry to trouble you.
But, if as you say, it comes and goes, it wouldn't be a detached retina. When that happens, the black curtain just stays there - it does not just appear at certain points in the day, e.g. in the morning.
You know, I just though of something. If it appears just for a few moments when she first gets up in the morning, it might not be an eye problem at all. It could be just orthostatic hypotension. It's a brief, usually harmless drop in blood pressure when you stand up suddenly. I've had it all my life. When I was younger, I thought it was something wrong with my eyes, because the only thing I noticed was that part of my visual field goes black. Then I just wait for it to clear, then go about my day.