Go Island jumping!
One of the best things about vacationing in Hawaii is the fact that the different islands are within close proximity to each other. If you are staying on Kauai, and you want to see Pearl Harbor on Oahu, it's simply a matter of choosing to do so. There are several tour companies that specialize in neighboring island tours that will whisk you from Kauai to another island; show you the most popular attractions for a day (or let you explore on your own); and then take you back to Kauai before bedtime. See the best attractions.
Taking a tour to a neighboring island allows you to see the best sites on the other Hawaiian Islands, without having to spend your entire vacation there. Do you want to visit historic Pearl Harbor? Then take a tour that allows you to spend a day at Oahu's premier attraction. Want to immerse yourself in Polynesian culture? No problem - there's a tour that will allow you to do that as well. It's easy to see another Island from Kauai, and it's fun.
The neighboring islands you can currently visit are listed below:
Kauai to Oahu Arizona Memorial, Pearl Harbor & USS Missouri
Neighboring Island Tours from Kauai are very popular, so be sure to make your reservation early.