If you have what it takes (namely, no claustrophobia), you’ll enjoy venturing up to 100 feet below the sea in a 65-foot submarine, with a large porthole for every passenger. During your 45 minutes underwater, the sub glides slowly through an 18,000-year-old, 25-acre coral reef in Kailua Bay, teeming with schools of colorful fish (including, unfortunately, invasive species such as goatfish and taape) and two shipwrecks encrusted in coral. You’ll take a 5-minute boat shuttle from Kailua Pier, across from the ticket office, to the air-conditioned submarine.