Not a SEAL, but my father was a frogman during Vietnam.
He has told me a few stories, but mostly keeps quiet about it. It has already been said a dozen times, they kick your ass until you break and then keep on going.
They know when you get into the real "conflict" settings, the duration of those operations can last days without any sleep at all. Better to see how you'll react in training
than on gameday. Besides you don't want someone from your team to fly off the handle and crawl up in the fetal position in the middle of the operation.Remeber that scene in the Dirty Dozen where Telly Savalas goes nuts and they his own men have to kill him.
Besides, it's very expensive to launch a special forces operation...esp. without congressional approval. Sometimes they are deployed by air drop, long range lt. weight water craft,submarine, or a combination of the last 2 mentioned.
This gets to the essence of why they are SEALS.
A few things that stick out from my fathers training was the exposure in water...get used to cold water, cold showers, shivering etc. He said towards the end they were required to assemble car parts 10-15 underwater blindfolded.
They also used to make his group of ~8 carry around a telephone pole for days...splinters in all...not a time to pause and say ouch.
One of the final training exercises was a random one.
In the middle of the night while 1-2 miles of the coast of FL on a frigate or something, they woke them up and threw them off the ship and told them to make it back to shore.
Upon impact with the water, he was bit by a Portugese Man of War(jelly fish) and popped his eardrum. Which leads me to believe that my father was never sympathetic after one of my "long runs".
They also require a considerable amount of SERE training which gets at the psychological aspects that people were talking about. They will beat you up and see how well you can take it. They don't care if they break your nose or you lose a tooth.
If you're superfit it's a bonus. Also helps if you know 2-3 languages, preferably arabic, russian, korean or chinese and are very tech savvy. This may ensure a support role on 1 or 2 SEAL teams that operate in the same theater.
I'm sure it's nothing that you haven't heard or can't find out on the internet. Good luck...you're a better man than me.