Expanding on what you said, the top 10 metres are by far the most dangerous due to rapidly dropping air pressure in the lungs causing shallow water blackout. Fo

Expanding on what you said, the top 10 metres are by far the most dangerous due to rapidly dropping air pressure in the lungs causing shallow water blackout. For serious freediving, your partner meets you at -10m as you ascend. This can clearly be seen in the fantastic william trubridge arch video. [1] It's quite common for an instructor to dive alone with students. Even a first level freediver knows how to save someone from a shallow blackout; it's unclear if her diving partners were suitable or if she took excessive risks. This is a good reminder that no one is invincible. [1]https://www.youtube.com/watch?v=hrXQbucZUDA https://www.youtube.com/watch?v=hrXQbucZUDA