Required - "Applicants must have a high school degree or GED, the ability to work in the U.S., English fluency and be at least 21 years of age"
These things will give you a better chance but it's not the end of the world if you don't have these things -
"The best resumes will include:
- One plus years of work experience in personalized customer service, patient care or similar role
- Experience in a role ensuring the safety and/or care of others
- Completion of a degree beyond high school or GED
Delta is also seeking language of destination applicants who have fluency in English and one of the following languages: Czech, Danish, Dutch, French, Greek, German, Italian, Japanese, and Korean. "
I haven't found anything about swimming requirements but they state that they have "rigorous training" so it might be part of the training process.
These are just the requirements they have currently so it might change slightly by the time you apply but it won't change by much if at all.
Also I checked 2 different pages for this info and one of them says 21 and another one says 18 to apply, neither of my sources are straight from a job description for a Delta flight attendant though, they're only articles for guidelines however the article stating 21 is by Delta so i'd probably trust that one more until we can find an actual job description!
Remember, even if you won't be able to apply for a few more years it's never to early to look up jobs going there currently, because the most useful information you'll find will be in there so you will know what sort of things to expect when you do finally get around to applying :)