Blacking out while freediving is much different than the type of "blacking out" you normally would associate with sport injuries.

It's an evolved response the body does to conserve oxygen use in the brain. Consciousness shuts off, but the brain is still active. For example, someone who blacks out this way will not get water in their lungs--a part of the brain that is still active keeps your mouth shut so that no water is accidentally inhaled.

Freedivers try to avoid blackouts, but in this context, there are established safety procedures and it is not nearly as bad as you may think.

You're talking about laryngospasm:

https://en.wikipedia.org/wiki/Laryngospasm

Before laryngospasm occurs water must enter the larynx. At which point, if you 're a few meters under the surface of the sea, you're in the process of drowing.

Think of it this way: if it were safe to lose consciousness underwater, if we had a magickal reflex response that kept us safe- why would anyone ever have to drown?

Forgot to mention if you listen to accounts of blacking out while freediving, it's clearly much different than a physical concussion. People wake up as if they just had a deep nap, with generally no symptoms as the day goes on.

I did not said I think it is like concussion. I said that I find it less likely it does not affect the brain in the long term.