If a 1 month old baby turns his head in the bath and his face is submerged for just a moment, and then he coughs once and spits out a little water - is this dangerous or an emergency? even if he seems fine and has no symptoms after?

If your son is otherwise healthy and has no respiratory or feeding difficulty, this brief episode is not likely to cause further problems. There is though a small risk of aspiration. Watch for signs of respiratory difficulty, cough,fever and problems with feeding. Schedule a visit with your pediatrician. A virtual consult with Healthtap is available. Using less water in the tub is recommended.

As long as he is asymptomatic and back to normal self and feeding as usual, that should be ok. You can continue to watch his breathing and if breathing normally, infant should do well. But if any doubt, you may want to make sure that you follow up with your pediatrician

The baby had an entirely normal response to having his face submerged. If he looks fine to you after this momentary submergence, then he really is fine and you do not need to worry. I would be more worried he did not respond to the water on his face with a cough and a spit.