Obviously what is available to do as activities will change depending on which island you visit.
But let me make some general observations about what are the best activities in Hawaii and then I will make some island specific recommendations.
Here is what you absolutely must do in Hawaii:
Go to the beach walk barefoot take in the scenery try some local food (this includes fresh tropical fruit, hawaiian cuisine like plate lunches, and local japanese food like bentos and musubis – best found at a farmer’s market) swim in the ocean watch the sunset see an authentic hula dance (lots of free ones in touristy places like Waikiki beach and shopping outlets near big hotels) relax sleep in slow down get on a boat smell some flowers snorkel see dolphins (from shore if you are lucky, or from a boat)
Here are some island-specific recommendations:
See the volcano somehow whether by driving up to the summit or down to the lava flow or by flying over in a plane or helicopter Best Boat Tour on the Big Island and in all of Hawaii, in my opinon: Fair Wind see a black sand beach – try Punaluu
go to Pearl Harbor go to Waikiki beach even if only once check out the North Shore especially if the waves are pounding (which they do in the winter) Best Boat Tour on Oahu: Sail Hawaii
(I don’t consider Haleakala a must-do. It’s ok only, in my opinion) Lot’s of the super cool stuff is in Hana or on the road to Hana, and that’s quite a commitment to recommend, so I say just enjoy the island – check out Kaanapali beach for sure) Best Boat tour in Maui: Pride of Maui
Best Boat Tour in Kauai: Holo holo charters The Na Pali Coast is pretty cool
What about you?! What is your favorite activity in Hawaii!? What MUST a visitor do, in your opinion?