It's still too early to think about swimming. Your most important job right now is resting, so your knee can heal. try not to think of it as "doing nothing" because you aren't. You're working hard at resting, to give your knee the best possible chance of a good recovery.
It's unwise to go into the water until your incision is completely healed, with no scabs and no open areas. You would be risking introducing some infection if you did it sooner.
You can start water therapy later, but do take it gently. Just start with floating and walking in the water. Later, you can introduce a few exercises. Actual swimming, especially the leg kick, will be difficult for a while.