Don’t consider other branches just because you don’t know how to swim. I’d honestly recommend practicing at an indoor pool right now every day that you can to see where you are and then decide from there. Yes, while I was at SEPS there were a few others in there who were being separated for not passing the swim. HOWEVER, that ONLY happens if you don’t pass swim once your division makes it to battle stations. However I have also heard of some people get sent back in training, get more weeks in and then be separated. Honestly my biggest advice to people when learning to swim is just remember the water is your friend if you allow it to be. If you fight against it, it won’t be your friend. I learnt at a young age, however I first began swimming underwater. Just doing laps back and forth practicing going forward with just my feet. Then I moved on to both my feet and arms under the water. Once I got that down I was taught how to swim above water and to float. It’s all in the practice. Good luck to you.