Stew Smith has long been "the guy" for people that are wanting to be Seals. He has some great books out there- my favorite is Maximum Fitness. Any of his ebooks will help you except maybe the beginner program if you are already in pretty decent shape.
Here is the page for the 12 week program.
He also has a free workout for every week. That can be found here. If you want to go this route, it would be wise to back up and do the first week first and just progress through his plan. He is currently on week 17 and there is no need to try to get there before you go through weeks 1-16 even though it isn't necessarily a progression type thing.