I just asked my teen who did the course and she said she was required to wear socks. She had a really fun time doing the course with the friends she made on the ship.
You don't need to register, you can just show up. I'd recommend getting there close to the start time since the line got long fast. About 10 minutes from the end they did a "last call" for the line. It was fun! My husband and I did it once and my son did it about 5 times.
The obstacle course was fun. Seems like it was up most of the Nassau day on our 3 day cruise. You do need socks and I think the height minimum was 40 inches. When we showed up about an hour after it started the line was probably 15-20 minutes.
GET UP TO A $1000 SHIPBOARD CREDIT AND AN EXCLUSIVE GIFT!
If you make your Disney Cruise Line reservation with Dreams Unlimited Travel you’ll receive these incredible shipboard credits to spend on your cruise!