I am a certified diver but have not taken any freediving courses yet. Sometimes I try to hold my breath. My longest right now is 2 minutes. I recently was attempting an apnea walk when after about 10 seconds I blacked out. I woke up confused a couple seconds later. People around me said it looked like I was having a seizure, I assume that I was actually having full body convulsions? If anyone can help me out with this I would appreciate it. I'm just trying to figure out what went wrong. Thank you