Hi! Being a competitive swimmer, I have tried it all - I find that using a clear top coat over the nail colour is the best fix. Also, make sure your nails remain moisturized - the pool as well as nail colour tends to dry nails out. I find that nail colour will last longer when nails are in better condition. I would try O.P.I.'s clear top coat and Sephora's cuticle oil pen. I hope that was helpful!
For me, there are 2 brands i like for swimming.
The cheap version- Sally Hansen "Hard as nails" polishes.
The more expensive version- OPI nail polishes.
They both come in lots of cute colors that look really pretty underwater!
ph07 has provided you with excellent advice! A base coat and a top coat will always help in making sure your nail colors last longer. OPI's 3 Nail Treatment - 3 in 1 Base, Top, & Strengthener is a fantastic option. I often find that after swimming, taking a long bath, or washing my dogs that my cuticles are super dry. My favorite fix for this is Josie Maran's Aragon Oil, it leaves the bases of my nails refreshed.
A really cheap way to fix the fading and chipping is to get drugstore nailpolish with the thin brushes, and after painting them once wait a long time for the nail polish to dry. Apply a clear coat. The next day, apply another clear coat! If you apply several clear coats, the nail polish is practically indestructable (even when touched by nail polish remover!!)