Training for a 20+ hour swim

Hey Folks!
I am curious if any of you have done any swims that have taken over 20 hours? If so, was there any specific training (other than putting the miles in) that you did to prepare for that amount of time awake/in the water?
If noone has done a swim of that magnitude I would love to hear your ideas on what YOU would do to prepare for that.
Thanks!
Comments
Include these in your program:
Good luck
Wow, Thank you! That is great advice. I appreciate it alot!
On the longer sets try to develop patience and pace. For example, instead of trying to hold 1:15 on 1:30 intervals, slow down to 1:25. You need to learn to swim slower then normal while still keeping form.