Have an "accident" in the pool

You're gonna have an accident in the pool!" Cathy said.

"No i'm not going to..." Katie said, but she was interrupted by a stern expression.

Katie sighed and walked to the nearest pool. People were keeping their eyes on her but there was no way anyone would see her pee in the water. Besides, in water less people would see her naked so it was smart to go there anyway.

Katie jumped into the pool and swam for a minute. Cathy was keeping a close eye on her from the shore. After two minutes Katie decided it was time and she relaxed her muscles. She started to pee slightly and she pushed it out a little more. She started swimming a little to let the pee spread out more easily but then she heard people shout at her and she looked back.

Behind her was a clear red trail visible as if she was bleeding. This wasn't her time of the month, what was happening???

From the shore a pool guard called her out of the water with an angry face. People around Katie were still staring at her as she shamefully made her way out of the swimming pool.

"You peed in the pool?" the man asked her. He didn't even care about the fact that she was naked.

"People do that all the time right?"

"Not in my pool they don't. The water colors red when in contact with urine. There's warning signs everywhere!"

"I'm sorry it was an accident sir..." Katie mumbled.

"Here, come with me, i'll bring you to someone to help you." the man said with a more caring voice.

He brought her to the First Aid and talked to the nurse there.

"This little girl just had an accident. I think her parents let her swim without a diaper."

"I see" the nurse replied. She walked up to Katie. "What is your name?"

"I... i'm Katie"

"I see Katie, did your parents not bring any nappies for you?"

"No you see..." How was she going to explain? How old did this woman think she was???