How easy is it to island hop between the Hawaiian Islands?

Air travel is by far the most practical option. The "superferry" went out of business years ago. The inter-island flights themselves are short, generally less than an hour, but keep in mind that any air travel involves spending a lot of time at the airport going through the check-in and security. If you're planning on flying to another island and flying back the same day, you probably won't be able to spend enough time there to make it worth the hassle. I'd plan on at least spending the night there. My best island-hopping vacation was a trip to Kaua'i and Maui. I spent a whole week on each island. Airlines like Hawaiian Airlines give you the option to book a multi-destination vacation where you can fly to one island, fly to another, and fly home from the second one without going back to the first one. It's cheaper and less time-consuming that way than it is to fly from one island to another and back before returning.