While on the big island, we stayed at the Hilton Waikloa Village! This place was massive, so big, in fact, that you took trains or boats to get around the 62 acre resort. The resort had three separate hotels, 3 pools, an ocean-fed lagoon, several restaurants, and several dolphins on the property. We snorkeled in the lagoon a few different times - we saw sea turtles, Humuhumunuknukapau, and eels. We stayed out there each time for hours on end and seeing all the different creatures swimming below you was a magical feeling.
Snorkeling has always been a favorite for us while traveling to Hawaii - we've gone off of Molokini, Turtle Town, Kaanapali Beach, and Black Rock Beach. One time we could even hear whales underneath the water.
While on a tropical vacation -- Snorkeling is a must!!!!