For myself, swimming can turn fat into muscle and make the whole body muscles firmer. The whole person will appear very mentally healthy rather than lax. If it is 1500 ~ warm up for about 500m, slowly stretch your muscles, and then swim in groups of 800m (for example, 6 25m sprints as a group, and take three deep breaths every 25m). You can swim in five groups, with a break of 30 seconds between each group (to 1 min), and swim slowly for the last 200 meters, so as to prevent lactic acid accumulation and muscle agglomeration and hardening, which is helpful to lengthen muscle lines. But be sure to stretch. This is probably the suggestion. It may be a little difficult, but stick to it and you will get something that surprises you. I hope I can help you.