Dumb swimming lesson question

elmoali

Aiden has his first swimming lesson on Saturday  I know rash guard's primary purpose is to protect against the sun.  But does it serve any purpose in an indoor pool like to keep him warmer?  I don't really see how since the water is going to soak the material but I've heard that some people do use them at indoor pools.

ETA:  I meant to post this on 12-24 but you're just as able to answer so no DD for me