Kailua-Kona
A national historical park 10 minutes from Kona that almost no tourists visit — ancient Hawaiian fishponds, lava coast, and a sheltered bay where Hawaiian green sea turtles rest on the beach in numbers that rival Punalu'u. The ʻAiʻōpio Fishtrap area is the focal point: a large enclosed lava pool used for ancient aquaculture, now filled with fish and surrounded by turtles on the rocks. Swimming is possible from a small beach in the protected cove. The combination of free entry, no crowds, and genuine wildlife makes this one of the best-kept secrets on the island.
Free, no reservation. Enter via Honokōhau Small Boat Harbor off Hwy 19, 10 min north of Kailua-Kona. Turn right on Kealakehe Pkwy and park at the end of the lot. The park entrance is on the right; walk ~5 min to reach ʻAiʻōpio Fishtrap.
Year-round. Turtles present daily. Midday can be very hot on the open lava — go in the morning.