My kid is learning to swim in 8 days. Start to finish. It’s a program that promises as much. He’s already very comfortable in the water and has spent lots of time in the pol but at 4 years old is still wearing a life vest in the water and sticking to the shallow end. In 4 days of this program he’s already jumping off the diving board and swimming to the bottom of the pool to pick up toys. The program presents him with small steps and then builds on them and it ends up being about confidence more than anything. Last night I was talking with a friend yesterday about the junior lifeguard program her daughter is in and the qualifications and training the kids are going through, I joked that it sounded like Navy Seal training for 16 year olds. She responded that their instructors are Seals.
This is a recurring thread with training, give people crazy challenges they didn’t know they could do as if they are no big deal, then when they complete them they will have the confidence to pull off the normal stuff they are faced with day to day. This may be useful for self conditioning as well, though I wonder if knowing ahead of time what you are doing defeats the point.