12 hours of pure hell and the hardest thing I have ever done in my life. We had a marine force recon guy on the team and he was saying it was just as hard as when he was in training. We had to do things like simulating looking for IED's, taking casualties, trying to make it to an exfil point under a strict time limit, wading through a river while on sound and light discipline (can't make any sounds or turn on lights) and so on. We also had to practice leave no trace behind and were not allowed to let anything we were carrying touch the ground the entire time (rucks, flags, team weights, etc..).
It gives me a new found respect for the special forces guys because we just did it for 12 hours with one night of sleep deprivation (I was up for about 36 hours straight), but those guys do it for weeks on end. You can see the photos on my FB page if you want an idea of it.
I will be moving on the to the GORUCK Ascent next year which is 100 hours of survival training in the mountains