$5.50 – $6 Climb Diamond Head. Admission is $1 per person and you can take the bus for $2.25 each way or pay $5 to park a car. Then you have to climb rather a lot (though I’ve seen grandmothers do it, and small children in flip-flops) for a spectacular view of Honolulu.
$4 Go floating at Waikiki. Buy a $3 air mattress or inflatable tube from any ABC store (they’re everywhere) and the store will inflate it for you for less than $1. Then head over to Waikiki Beach and get your float on. (If you don’t require artificial flotation, this experience is free.)
$4 Chill beachside at the Hilton. Last I knew, the pineapple juice refills were free at the Hilton Hawaiian Village poolside bar, with a great view of the beach. Sometimes there’s live music, too.
$12 – $25 Snorkel at Hanauma Bay. Entrance to the Hanauma Bay Nature Preserve, which offers excellent and gentle snorkeling suitable for beginners, is $7.50 and the bus fare is $2.25 each way. Snorkel gear will cost you about another $12, if you rent it there. If you don’t want to take the public bus, Hanauma Bay Snorkel Adventure will pick you up at any Waikiki hotel and provide gear for $17, not including the $7.50 admission fee.
$0 Waikiki isn’t just about the beach. Head a few blocks back to the Ali Wai Canal, an excellent place for a stroll at dusk, when the kayaks and sculls are out on the water.