disclaimer: I am not (yet) a freediver, rather I swim underwater. The sixty foot dive below is my deepest and at the time I knew almost nothing about freediving.
A question like this is highly dependent on the individual answering it. I can imagine being capable of comfortable plunges to 150ft. and thus thinking nothing of free-swimming a reef to 80ft solo. In reality (for me) One day I decided to see how deep I can get on breath. Between dives (scuba) I jumped in the water alone. I will add, I frequently dive alone and I think there is more risk freediving solo. I dipped under and headed for the bottom (thankfully only 65ft down). Upon reaching the bottom, I felt surprisingly well. I swam along for about 10 more seconds, and turned to the surface. Almost instantly I realized I would have a hard time making it back up. This is the second time in my life (40yrs) I had been truely scared in the water. A few seconds later I was thinking "how devestated my son was going be" and I was sure I wasn't going to make it - absolutely sure. Fighting the constant, rapid contractions and "reaching" for all I was worth I broke the surface. Though I just wanted to gasp massive gulps of air, it was almost hard to breathe and the first breath actually took a couple seconds to acheive.?! This, is the epitomy of stupid in my opinion and I won't be trying that again - alone away. I will however take a cruise down to 30ft or so (for now anyway). Pushing the limits is always potentially deadly. Not knowing your limits IS deadly.