weird guy people think I have a crush on

So apparently all the guys on my swim team think I like this one dude (let's call him John) and they all talk about it in the locker rooms because he's in my lane and will sometimes talk and he'll also go next to me if we are kicking and talk to me but I like this other guy on my team (let's call him Alex) Alex is nice and not that weird and john is kinda annoying and like really weird and will always talk about pop tarts or if he has to go to the bathroom. It's really weird so I just kick faster to pass him. So I like Alex but never really talk to him because well I'm really shy and don't usually talk to people at all. How can can I make them think that I don't like John because I don't want people to think I have a crush someone that I don't