Water is circulated all the time in the air and oceans and the water on land. The stuff you want to worry about is sulfur and nitric acid raining down after say a meteor hits the Yucatan area by Central America like one did when it wiped out the dinosaurs. It hit an area that contained lots of sulfur.
Yes, but...
NASA and the EURO Space Agency agree that this underwater eruption added from 10% to 30% of water vapor, which holds heat.
Sounds like a dramatic escalation.