[The Killer's me]

Indeed you will be putting your ass on the edge by diving alone.
what Marwan mentioned on Top, it is all true...
Dont push the limits, take good rests between dives. Never hypervantilate.
If on the way up, your shaft got stucked inbetween the rocks, leave it and make another dive after taking enough rest.

Happy diving and try to take a freediving course to know more about this sport.