If you are 24 years old and 140 pounds, and swim a lot but do not lose weight, it may be attributed to your metabolism. Also, when our bodies are used to a particular workout or regimen it tends to do what is considered "peaking" meaning that you may need to add some additional movements to your work out. Try mixing swimming & weight training. You can also lower your caloric intake to see a difference.
The weight that you are caring know is Turning into muscle the only way to cute down is to eat only one solid meal a week then it at least 2000 calories a day . Drink lots of water less sugar less butter products or dairy products. If you still get hungry then eat a apply or orange or steam veggies .