Walk south from any point in Honolulu and you'll soon find yourself standing on the waterfront. Hop in a car and the same is true of any direction—you can make it from downtown to Makapu'u Point on the east end of the island in about 30 minutes, and to the North Shore in 60. The shoreline is the defining feature of the area, so many of the things to do in Honolulu relate to the water: snorkeling in it, surfing on it, or even simply admiring its beauty.
Drinking in the view is all that seems to interest some of the sunbathers at Waikiki Beach, though other beachgoers find ways to keep themselves occupied—say by boarding a catamaran and sipping on cocktails during a sunset sail, or hopping in an outrigger canoe with a few friends to paddle across the shimmering waters. To see what those waters hide, rent some scuba gear and hire a guide to take you 50 feet below the surface, where you may encounter eels, sea turtles, and, with luck, a Hawaiian monk seal. Some scuba tours will even take you down to explore the area's shipwrecks, many of which were sunk on purpose to create artificial reefs.
A short drive from the shoreline lies one of Hawaii’s most storied natural attractions, Diamond Head State Monument. Don't be fooled by the name—the "monument" isn't a statue or plaque, but a crater that stretches 760 feet across. Named for the twinkling crystals British sailors discovered there, the 100,000-year-old natural phenomenon contains a hiking trail, underground tunnels, and long-abandoned military bunkers.
These bunkers point to an important part of Hawaii's history: its role in hosting U.S. military bases. The U.S. Army Museum of Hawaii examines this role in exhibits such as "Defending an Island," which explains the strategy and technical challenges behind building the batteries that protected Hawaii from invasion during World War One. The museum of course also covers the December 7, 1941, attack on Pearl Harbor, though you may want to simply see the site of the attacks for yourself. Do so by scheduling a Pearl Harbor boat tour, which might include a visit to the USS Arizona Memorial, a 184-foot hall that sits suspended above the sunken warship.
Two relics of Oahu's past open their doors to the public in downtown Honolulu: Kawaiahao Church and Iolani Palace. The former, dubbed the “Westminster Abbey of the Pacific,” dates back to the mid-1800s, when Christian missionaries and natives lugged 14,000 coral slabs from the ocean to construct its walls. Iolani Palace didn’t appear until 1882 at the behest of reigning monarch King Kalakaua, who regularly hosted parties in the extravagant dining room. Given his penchant for entertaining, the beloved king might be glad to know his home continues to welcome plenty of guests, though now as part of tours, not parties. On these tours, visitors ogle the extravagant koa staircase, the detailed furniture, and the portraits of Hawaiian kings and queens.
The waters of Honolulu offer some of the most unique sea creatures in the world, and there are many fishing and snorkeling tours available.