Snorkel Bob's is a great place to rent gear (snorkel, boogie board, etc.). Prices are good for both single/multi-day, you can purchase insurance, there's a wide variety of products. It's on Kapahula & Date. If you want to try Hawaiian food, a luau might be a good option. It's an investment of time and they can be corny, but I'm sure there are some that are well worth it (the one I went to with my family at age 15 wasn't).