Swimming is a big part of my life. However, when I put my swim cap on I get an erection. Is that normal? It's so clear to see my erection with my speedos on. I have tried not wearing speedos and a swim cap. But in my races I have to put them on. What should I do?

This is not normal, do swim caps turn you on somehow ? Masturbate before you go perhaps ?

If this gets around, there will be a run on swim caps.
Seriously, if it is critical for you, you should consult a urologist. Erections are closely related to blood flow. Some people complain of headaches caused by swim caps. Maybe there is a medical reason for your problem possibly involving blood pressure.