The reason why drowned aren’t spawning in the dripstone caves is due to an error in the spawn code, for dripstone caves, the drowned are set to “spawns_on_surface” instead of “spawns_underground”, which means they will only spawn in dripstone cave aquifers exposed to the surface. Changing the “on_surface” to “underground” fixes this and allows them to spawn, but preferably, simply add “spawns_underground” below spawns on surface allows them to spawn in all dripstone cave aquifers regardless of if there is air exposure or not