Is it normal to be sexually attracted to a stanger?

Okay, so i have this major crush on this guy from school. I know we would be a good couple, and I know a lot about him because we use to be buddy's. But we have P.E together and the past few weeks was swimming. and he is so hot, and really good on the diving bored. But every time I look at him, I get horny. And every time he talks to me, I get really nervouse and don't know how to reply. But the main point here is that, I want him to do something funny with me and mayby play with me a little. I just really get horny with him. I really want him with me all the time. Someone help me out.