Aroa Marine Reserve occupies the lagoon area immediately adjacent to the Rarotongan Beach Resort and Sanctuary on the Beach Resort in the Aroa locality of Puaikura.  Fishlife is abundant, due to human intervention, and is representative of fish life found around the southern lagoon area of Rarotonga. 

The owner of the Rarotongan Resort was a primary instigator for the lagoon area to receive protective status during the mid '90's.  In conjuction with a group of the island's traditional leaders and landowners for the surrounding area, marine protected areas were initiated in several areas around Rarotonga under the guidance of the Koutu Nui group of traditional leaders who helped raise public awareness about the importance for restoring depleted habitat for the future viability of marine resources,  but also to offer education for young Cook Islanders about their heritage.  From five representative lagoon areas initially selected under a Ra'ui status for Rarotonga, the Aroa -Rutaki ra'ui was one of the first protected areas to receive recognition and protection. 

Some of the colourful tropical fish a snorkeller can expect to view in this lagoon area are parrot-fish, wrasse, angelfish, butterfly-fish, blue starfish, sea-urchins, sea-cucmbers amidst other species that frequent the tranquil waters of Aroa. Boating (motorised) and fishing are not allowed within the reserve.