I get it too if I don't drink a lot more water. So did many people on my sports team.

Creatine binds to water (making less water available to your muscles) and allows your muscles to work harder (which makes them need more water). So if you're not drinking a lot more water when you're taking creatine, you will get cramps from either dehydration and/or muscle overuse.

But once you're past the loading phase for creatine and getting sufficient hydration, it's supposed to lessen cramps because the water bound to creatine also becomes available for use again as the creatine is used by the body.