Okej I understand.
Btw you're English is fine
Well, the differences between the ocean and the pool is a LOT. First of all when u swim dynamics in the ocean, the waves, and currants always interfere with the gliding and concentration. Naturally this makes it harder to swim dynamics in the ocean.
To be able to swim deep is a whole other matter than dynamics. You body has to cope with doing some hard kickings to get deeps where it starts to get easier, this burns oxygen. Also pressure from the ocean deeps are affecting you almost directly, you also need to equalize correctly, also the stress levels are often higher. As you can see the list can be made long. And there are several thing I don't write now.
Happily, there are several ways of practicing this to get better at deep diving, and luckily I'am going do a BIG tutorial on this and much more on my YouTube channel! I'm already working on it and part 1 should come out soon.
Hope my post helps you a little bit. You can see my channel below. Subscribe if you can so you will be up to date when I release the videos.
Be safe and have a great weekend freediver friend!
Best regards Youbuur
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Check out my freediving channel on youtube.
[ame]http://youtu.be/U2wGLXjEJv0[/ame]