My sister swims for exercise, and asked for a waterproof ipod shuffle for Christmas. I thought she was joking, but they do actually exist. Apparently they are quite popular at her pool:
I can confirm the 'waterfi' ones work as they claim. Got one for my mom since she does hours of swimming a day and said it was boring without music. The buttons apparently are very mushy (no click to let you know you pressed them) but it functions fine.
http://www.amazon.com/s/ref=nb_sb_ss_i_0_18?url=search-alias...