Old Kona Airport is a very good dive, 2 Step (Place of Refuge) Should not be missed (get there early for good parking). Mile Marker 4 next to Magic Sands Beach is a good spot right in the middle of Kailua Kona you can do multiple dives at 2 Step and not get tired of it, and if you are into Hawaiian history at all The actual Place of Refuge is Fascinating to go check out after you are done diving for the day. Also you could kayak your dive Gear over to the Captain Cook Monument on Kealakekua Bay, But it is a long paddle, Even if you just snorkle there it is WELL WORTH IT! Look up Ehu and Kai Kayaks on line, Me and My Family rented a kayak from them. It is a Hawaiian Family run operation they own a house and land right on the bay and you basically paddle out from their front yard. Otherwise you have to lug a kayak down to the bay on top of your car. The Coral Reef at Captain Cook Monument is VERY NICE, lots of fish, Spinner Dolphins,I did a bunch of freediving there. Bring a lunch but watch out for Mongoose (little thieves), 2 Step is very similar to this spot except your car is right there and you dont have Mongoose stealing your unattended food.