You can definitely rest assured that it won't get thicker as long as you train properly. I have been learning swimming since I was 7 years old, so I can share my experience with you. Breaststroke and butterfly are the least suitable for girls. These two moves require high strength, and it is easy to get fat if you stop practicing more. Butterfly will widen the shoulders, but breaststroke is not so obvious. The freestyle and breaststroke, which are most suitable for girls, have posture advantages, which make freestyle labor-saving and have obvious shaping effect. As for the time per week, it is recommended to have two or three times. I have experienced the situation that I stopped to get fat, mainly because I trained too much. If you don't train with a professional team, the amount of training won't be too large. You can rest assured. Don't eat too much after swimming, just drink water, otherwise it will be absorbed.