According to Wikipedia, freediving "is a form of underwater diving that relies on breath-holding until resurfacing". It's a sport I have practiced on an off over the years. I had been quite pleasantly surprised with my initial results under proper guidance: 4mn35 of static apnea underwater! It had happened during a week of travel in the Philippines with a former champion. I then did not have many opportunities to dive for a while, but I knew I had to explore this sport further.
Fast forward a few years. I am now booked for the AIDA 4 stars. It's the highest non-professional freediving certification. In order to get it, you have to achieve a bunch of things: doing 3'30mn of static apnea underwater, swimming 75m horizontally with fins, "saving" someone from a problem 25m underwater, going back from 25m without your mask and one of your fin. And also, going between 32 and 40m below sea level with only one breath-hold. It was going to be a big week.
I did not expect a few things though. I had a booking at the end of September. The water is getting cold at this time in Mediterranea, but I thought that it had to be ok if they organized training sessions during this period. It was around 16°C during the whole week. It's indeed ok − you can manage − but it's one more parameter that adds to the difficulty of this sport.
I had to do 3'30mn of static apnea. It's 1mn less than my personal best, but in a 16° cold water it was really hard. Jorgen tried with me. He has way more experience than me and can stay still underwater for more than 5mn. He gave up during his attempt and blamed his poor performance on the cold.
Freediving is a mental sport. Your body is the physical materialization of events that mostly happen in your head. In order to succeed, you need to want to succeed, and you need to be super relaxed. I lost track of time while trying to relax because of the shivers (I could not focus on being more and more relaxed), and it was super stressful not knowing where I was exactly. At some point, the urge to breath was really strong, and I wanted to get out of the water. But my trainer had his hand on my head, gently pushing on it so that I stayed underwater a bit more, yelling "just a bit more". He knew I could make it, but it added to the stress. At some point, I gave up and went out of the water. 3'45! Somehow, I had done it.