I know you were specifically asking about relaxed hair care and swimming but I thought I'd suggest this one anyway: Aubrey Organics' Swimmer's Shampoo & Conditioner
Aubrey Organics
My mother has natural hair but has found success using these two, which is a miracle considering how sensitive her scalp is to almost everything on the market! She's found the conditioner very moisturizing, which is great because her locs tend to dry out sometimes esp. w/the chlorine. Although I haven't used these two products specifically, the others I have used (GPB conditioner, J.A.Y. shampoo) worked wonderfully for my relaxed hair. If I started swimming, I would definitely consider the Swimmers Shampoo & Conditioner.