How do i look skinny in a swimsuit ? (10PTS BEST ANSWER)?

Wel im 13 , around 5'2 to 5'3 and im fat i dont want to tell you my weight but im not like a fat fat fat person im like fat i dont look that fat mostly chubby and i hate my thighs and arms , im going swimming this saturday and dont comment saying LOOSE WEIGHT how can you loose weight in 3 and a half days , my swimsuit is like a top and bottoms but the bottom bit of my belly shows , My belly aint too fat just my thighs and arms , please help me ?