Potent cinabar

Just like potent sulfur, it could be generated in conjunction with potent cinnabar, which would release a slightly reddish smoke and leave the water with a brownish hue when generated alone in water . Potent cinnabar could also cause poisoning or blindness while in water. This also adds a greater danger and challenge when exploring the sulfur caves. And it would also make sense since cinnabar has these properties in real life.