You might want to see your regular doctor or an Ear, Nose, and Throat specialist (ENT) about this if it is really bothersome. Your throat may not be closing all the way when you swallow. This happens a lot to people when they get older. They'll put thickeners in the water, milk, etc. so it isn't as easy to choke on. However, since you guys are so young, maybe something is abnormal with your throat. But I would think that if that were the case, it would happen more frequently than once or twice a year.
If it's not terribly bothersome, maybe just mention it the next time you are at the doctor for other things. In the mean time, make sure you aren't inhaling when you eat or drink, especially through your nose. Don't talk at the same time, either. If this happens while you surf, wear nose plugs and keep your mouth closed when the water hits you.
Also, be aware that this just happens to people sometimes. It may not be anything abnormal.