Aroa Rā’ui is a sheltered beach-access marine reserve on the southwest side of Rarotonga, set inside the lagoon in front of Aroa Beach. The route is simple: walk in from the sand, stay on the shallow reef and lagoon side, and treat the passage mouths as the boundary of the easy zone. It suits relaxed snorkelling and intro scuba work because the water is calm, the reef is close, and day-to-day planning is straightforward.