If the baby inhales small amounts water and he is normal active and playfull accepting feeds you need not to worry . If while breathing ther is grunting or wheezing sounds coming while breathing then u hv to keep a watch on him. Only problem can be to develop aspiration pneumonia that too it won't be so fast . It will show its symptoms after a few days with fever , cold cough , increase in respiratory rate . So for now u can do is chest physiotherapy --pat on his back And nebulization