If you're that weak, chances are they'll pick up on it before you get to the mile. At that point, they'll put you in a remedial swim class. You'll remain with your regular class and swim in the evenings. If you fail an event and its makeup, then you'll be rolled. I'm not sure if you roll back into the next the class or if you remain on some type of "swim hold" until you pass the event you failed. There is the potential of being "washed out" if you can't pass after the remediation. But, they'll work really hard on getting you up to standard -- if you're a poor swimmer, start working on that now. Don't wait until API.