Yes, there are volcanoes in the swamp biome. Hope you enjoy!

Thank you! And yes this was made in entirely in world painter (though the trees and stuff are mine and aren't available atm online). As for the reef, that was made by using the default 'cracked' brush and gently pulling the terrain up (Careful not to move the brush around too much or it will just be noise). Then I selected the coral block color I wanted (I have red coral reefs, blue coral reefs, and mixed reefs in that world for example) and painted the reef with the block ( be sure to select 'above' and input an angle so you realistically retain sand in flat areas). After that I just did a custom plants layer and selected the coral types I wanted and filled in the area.

I hope this helped!