Friendship problem... she gets mad alot?

I have this friend named Taylor. The other day we were in the pool and playing Marco Polo, and I kept swimming under water and she would open her eyes and go "You're cheating! You're not saying POLO!" and get all angry. Then she pouts and ignores me. Or she'll say something, and I'll say "What did you say?" because I didn't hear her, and I'll say what again and she's like 'Oh my god, I said _______!" and she'll pout. This has been happening alot. It's very, very annoying. What should I say or do?