What should i wear under my swim tights and swim shirt?

I have just bought stingray swim tights and a full sleeve swim shirt with uv protection to wear at the pool. What should I wear as my undergarments? I was looking for a sport bra for the top but I am afraid it would make me too heavy to swim. I am 34 C and don't wanna make my chest look too big under the water and I don't want my nipples to show when I am cold. Also, what panties should I wear? Any suggestions? Serious answers plz, no hipsy doopsies!!