Currency: The New Zealand dollar (NZD) is the official currency, used everywhere. Cook Islands coins exist but are largely collector's items. ATMs in Rarotonga and Aitutaki dispense NZD and accept Visa and Mastercard; expect a withdrawal fee of around NZ$5 per transaction. On the outer islands, ATMs are scarce or absent — bring enough cash before you leave Rarotonga.
Credit cards are accepted at most hotels and restaurants on Rarotonga and Aitutaki. Smaller guesthouses, market stalls, and outer island businesses are largely cash only.
Language: Cook Island Maori and English are both official languages. English is spoken everywhere relevant to travellers.
Time zone: UTC−10. No daylight saving time.
Phone and internet: Coverage on Rarotonga and Aitutaki is decent. The main provider is Vodafone Cook Islands; prepaid SIM cards are available at the airport and in Avarua. Wi-Fi is available at most accommodation on Rarotonga. Expect more limited connectivity on the outer islands.
Health: No vaccinations are required to enter the Cook Islands, though standard travel jabs (hepatitis A, tetanus) are sensible. Dengue fever is present but not endemic; mosquito repellent is worth packing. Tap water on Rarotonga is generally safe to drink. Medical facilities are basic outside Rarotonga's main hospital; serious conditions require evacuation to New Zealand.
Safety: Crime is low. The main hazards are reef-related — sharp coral and strong currents at reef passages. Reef shoes are useful. If you are swimming in the lagoon, stick to established swimming areas and stay inside the reef unless you know what you are doing.
Electricity: 240V, 50Hz. Australian/New Zealand-style plugs (Type I).
Sundays: Treated as a genuine day of rest. Shops close, transport runs minimally, and some areas are genuinely quiet. Plan meals and supplies around this.