Is it normal thinking my attractiveness keeps people from taking me seriously?

For some reason, nobody takes me seriously. For reference, I've heard from my friends that I have a fairly, ahem, attractive face and body. I've been told I'm very pretty and have quite the voluptuous body. And I'm not trying to sound arrogant, it's just important to the background.

I'm very intelligent and logical, which people don't expect from me. I take the most difficult classes, and I usually make the top grades out of each class. I also tend to be bubbly and talkative when I'm comfortable with the situation, which is usually an academic one. It seems like whenever classmates find out how smart I really am, they're genuinely surprised. Some of my friends even admit that before they started hanging out with me they used to think I was just a dumb blonde, not that they can explain quite why. New people I meet always assume I’m some ditz who’s lost in a group of nerds. At the beginning of every school year, teachers are surprised by my first high test grade.

This isn’t just academic though. Even as an athlete, I’m not taken seriously. I am a fantastic swimmer, and I perform well on my high school team. But when I wore a bikini once to a team party (I didn’t know I wasn’t supposed to), my (male) coach looked at my body and commented that “this isn’t spring break!” like I was acting slutty or something when in reality I was embarrassed about my faux pas. I’m also very social, so I know all of the younger swimmers and help them get to know the rest of the team. Whenever I’m seen talking to my teammates, though, my coach assumes I’m slacking and yells at me. He doesn’t even seem to care when I make a state cut in a new event because he doesn’t think I work to get it. Apparently, my improving times are all gosh-darn luck.

I am a smart girl whom people automatically take as a dumb blonde. I am a good worker and a fast swimmer but my coaches think I don’t work for my progress. Apparently, it’s just not feasible for me to be successful. Appearance is the first thing noticed, so do people automatically have me pinned as the “pretty girl?” Does this make them think I’m not the smart girl, not the funny girl, not the hard worker? Right off the bat, do people see me as unintelligent, two-dimensional, obnoxious, and conceited? Are my looks causing these perceptions and ultimately holding me back? If so, what can I do to stop it? Is this even remotely normal?