The watery diarrhea may be due to the acute gastroenteritis
which may be caused by bacerial or viral cause.
You should have the stool examination, stool c/s, blood counts etc done after consulting doctor to know the underlying cause.The oral antibiotics
like ciplox, metronidazole
etc are required for the bacterial cause.The viral cause is treated symptomatically.
You should also drink plenty of fluids to prevent dehydration