Bloating and diarrheoa after swimming

Patient: My 3 yo gets horrible stomach bloating and cramps after swimming. We have a salt pool but it doesn’t seem to make a difference what kind of pool she is in. As soon as we start swimming she gets bloated and not long after getting out she has to run to the toilet. After lots of screaming with pain she eventually has a massive explosion of diarrheoa and sometimes vomits. Please help