Sulfur and Sulfur Vents

Sulfur vents could be found at the bottom of deep cold or frozen oceans. These vents would spew out a yellowish gray smoke, and if something were to be placed above the vent, it would create sulfur scum. This scum would drop sulfur when broke or when the block above it is removed. Sulfur, when combined with charcoal, would create gunpowder. 

Maybe for renewability and easier farming, these vents could be created by placing magma at the bottom of a large body of water, and then using sulfur on it. 

This idea is to help peaceful mode players get a source of gunpowder, and also add a new use to the underused charcoal.