Honolulu & O'ahu: What to Know Before You Go

Short answer: book your three mandatory timed reservations for Diamond Head State Monument (30 days ahead), Pearl Harbor's USS Arizona Memorial (8 weeks or 24 hours ahead) and Hanauma Bay Snorkelling (strictly 48 hours ahead in the early morning Hawaii Time). Do not rent a car for your whole stay in Waikiki, where hotels charge steep nightly parking fees; instead, rent a car inside Waikiki only for the 1 to 2 days you drive to the North Shore, and pack mineral reef-safe sunscreen.

1. The 3 Reservations You Must Book Online

1. Diamond Head State Monument (Le'ahi): all non-Hawaii residents must pre-book a timed entry slot (plus a vehicle pass if driving) up to 30 days in advance at gostateparks.hawaii.gov, as walk-ups are not permitted.
2. Hanauma Bay Nature Preserve (Closed Mondays & Tuesdays): online reservations open strictly 2 days (48 hours) in advance in the early morning Hawaii Time on pros8.hnl.info and sell out within five minutes.
3. Pearl Harbor, USS Arizona Memorial Boat Programme: requires a small online reservation fee on recreation.gov, with tickets released 8 weeks ahead in the morning and a second batch released 24 hours before your visit.

2. Directional Words Locals Use Instead of Compass Points

On an island, residents rarely give directions using north, south, east or west. Learn these four Hawaiian words on your first day: Mauka means toward the mountains (inland); Makai means toward the ocean; Diamond Head means east; and 'Ewa (pronounced Eh-vah) means west toward Pearl Harbor.

3. Reef-Safe Sunscreen and Ocean Safety

Hawaii law bans sunscreens containing oxybenzone and octinoxate to protect coral reefs, so buy mineral zinc oxide lotion locally. Always check lifeguard flags before swimming, never turn your back on the ocean along rocky volcanic ledges or winter North Shore breaks, and give resting Hawaiian green sea turtles and monk seals plenty of space on the sand.