The sea caves along the Na Pali Coast, Kauai Specifically: Waiahuakua sea cave, Hoʻolulu sea cave and Open Ceiling cave
101 Free or Cheap things to do in Oahu!
A Mom's Guide: 15 Things to Pack for a Disney Cruise & Other Travel Tips - Harvard Homemaker
Swimming and interacting with dolphins at Sea Life Park Hawaii, Honolulu http://www.hawaiiactive.com/category/oahu-cat-sealife.html
When we finally make it over to Hawaii... we're eating malasadas from Leonard's. Must not forget this.
11 Places You Can't Miss In Hawaii (Oahu). A quick preview of the top spots you need to see on your next trip to Hawaii! - Avenly Lane Travel
Seahorse Farm tour, Kona, Hawaii You get to feed them and they'll wrap their tails around your finger!
A turtle sanctuary on north shore Oahu near Kailua . Anywhere you snorkle you can see turtles ( state law has restrictions as to how close you can get to them)
Inner tubing tour through the canals and tunnels of an old sugar plantation in Hawaii - add this to my bucket list!
Suggestions for a seven-day Oahu vacation itinerary | Go Visit Hawaii