Swimming is very safe in the sheltered lagoons but be wary around reef passages, where currents are especially strong. Rarotonga’s main passages are at Avana Harbour, Avaavaroa, Papua and Rutaki. They exist on other islands as well, often opposite streams.
Mosquitoes can be a real nuisance in the Cooks, particularly during the rainy season (around mid-December to mid-April). Use repellent, and mosquito coils are available everywhere.