I've read a lot that too much cardio will sabotage your muscle growth gains.
I swim 4-5 times a week for 30-40 minutes per session. But I'm also looking to build muscle as well. Right now I'm working out about 4-5 times a week as well and eating about 150 gs of protein a day and I weigh 200 pounds.

I'm just looking for advice on how to best balance the two for the best results.

I really wouldn't worry too much when it comes to swimming, primarily because swimming in and of itself is also a sustained resistance exercise. If you were looking to develop a body builder's body, then it would behoove you to reduce your cardio, but it sounds like you train to improve your swim (or else you wouldn't swim as much as you do). So long as you as getting in a full body regiment's worth of resistance training, you probably won't have to worry too much about defeating your resistance training with your cardio training.