It could have. Generally, this would be because of the bacteria in the water that small amounts of got ingested while swimming. It could also be unrelated.
You can try withholding food for the next 12 hours, but making sure your dog has plenty of fresh water available. Then start with a bland diet of boiled chicken or hamburger meat and white rice in a ratio of 1:1. Continue this diet for 2-3 days or until diarrhea is all cleared, then gradually switch over to her normal dog food diet. Some people also use pepto for the stomach inflammation at a dose of 2 teaspoons per pound per day (split into 2 to 4 doses throughout the day); I prefer just the bland diet approach, as pepto generally doesn't work very well in dogs.
Hope she's feeling better soon. Good luck to you both.
Christine
Veterinary Technician
Licensed veterinary technician (B.S. Mercy College), 10 yrs in animal medicine and training