Vai Marere is the only sulphur cave pool in the Cook Islands, a short walk from Mangarei village along a track through the makatea. The water is warm and mineral-rich, with a faint sulphurous smell that dissipates once you are in — locals have long attributed healing properties to the minerals, and the pool sees regular use by the island's small community.
The cave itself is smaller and more intimate than Vai Nauri, with pale limestone walls and stalactites framing the pool. The water is calmer here, making it a gentler swim than the deeper main cave. Visiting both pools in a morning is easy; the walk between them across the ancient raised coral is itself an experience, the makatea surface pitted and sculpted into fantastic shapes by millennia of weathering.