My toe nails have been falling off nothing is painful and it seems like others are growing in after them i am in college and play water polo and swim ?

Let them grow in: If you have no pain, bleeding or infection i would not be concerned. If you have fungal or deformed nails, being in the water so much might hydrolyze them and cause them to fall off if this is a bother you can talk to your podiatrist or dermatologist. Using an ointment (vaseline jelly) might provide a barrier to keep some excess moisture out might help/.

Trauma: It sound like yournails are responding to trauma. At least there is no pain.