Marvelous snorkeling and diving adds yet another dimension to the beauty of Rarotonga. The reef fronts the shore to the North of the island, making the lagoon there less suitable for swimming but to the south east, particularly around Muri, the lagoon is at its widest and deepest (2-3m).
Muri Lagoon offers many tropical fish and coral to view without strong currents and waves. Ask the locals where the best places are. There are a number of Dive companies in Rarotonga where you can get all the necessary training to have a safe and enjoyable dive.