Is this normal? Please help me

During my 7th grade year I became really good friends with this girl in my grade. It got to the point where we would stay at each other's house every weekend and even every day in the summer. We'll call this friend, Sally. Sally had a step dad, and we'll just call him Bob. Now Bob was a family friend, my parents trusted him. But the more I started to stay at Sally's house, the more comfortable Bob got around me. They lived on a lake and so we'd always go boating. Bob would always slap and grab at my ass. He always tried to tug at my swimsuit and untie the strings. He always told me how beautiful I was and how amazing I looked in my suit. He always wanted me to sit on his lap and he'd rub his hands all over me. He'd rub my thighs and my ass, and slip his fingers under my suit. I tried to tell my parents but they didn't believe me. They still don't. Is this something to be worried about or am I just over reacting? Please tell me what you think