swimming

I bought my girl to swim at the coast last week. it was her first time swimming at the shallow end. however, once she swam to shore, she started coughing out white foamy stuff and subsequently vomitted twice within an hour. subsequently she is fine otherwise I was about to rush her to the vet. is it common if the dog had ingested sea water? what other precautions should I take in the future. thanks for this informative website.