Most of the Kona side dive operations operate out of Honokohau Harbor, giving access to dive sites from Kailua Bay to well north of the airport. These are the operations most divers visiting the Big Island are familiar with. The diving is good around Honokohau, but can be limited, island divers know that the character of the reef is different as you move north or south.
Experienced divers will often recommend diving the Puako and North Kohala reefs. Here the shoreline is notably older, where the volcanoes have not sent lava flows into the sea for many thousands of years. The reefs have had much longer to establish themselves, resulting in heavier coral growth and rich sea life.
If you want to try the sites further north, along the Kohala Coast, you need to choose another outfit to dive with. Two local dive ops operate along the Kohala coast, Blue Wilderness and Kohala Divers. Both outfits are small businesses, locally owned and operated, the owners often on the boat with you.