I want too be a united states marine?

If it is what you want to do then you need to do it. If you still want a college degree there is the possibility of getting it while in the military. Don't stress yourself out too much about running and swimming. While it may be easier if you can pass all the PT stuff with flying colors, it is not required...just be reasonably in shape. Good for you on considering service, you won't regret it.