What Did I Do To My Calf Muscle?

I was at the pool earlier today and was on an inflatable platform. This kid that was 2x bigger than me got pushed off and was pulling on my foot (his hand was on the achilles tendon and on the top of my foot). I was pulling away and my calf muscle (the one in the center of your calf that goes from the center of the knee to the achilles tendon) started hurting. I gave up and fell into the pool. It hurt to move it and remained swollen (it felt flexed) and it hurt. What did I do to it? It still hurts.