Flirting with girls in pool party help?

Okay so im a guy and since it's really gettin hot this summer me and mi friends decided to ask girls from our grade that we are friends with, to see if we can jump in their pool with them. We don't wanna do anything sexual cuz they're just our friends( and were 14) But they wouldn't mind flirting or even some mild touching. So I was thinking since I hav a light tan and got kind of a six-pack and broader shoulders in the past year, should I be shirtless when talking with the girls? Or would it come off as kinda cocky? Ur probably thinking who would go with a shirt on to a pool, but in these pool parties we first talk or hang on the patio and we sometimes don't even go swimming at all and instead we just hang out. So should I be shirtless when just talking to the girls and would it make them want to get my number or ask me out? I would really really appreciate ur answers and points go to the best one! =]