Ala kaha kai, meaning "shoreline trail" in Hawaiian, is a 175 mile long trail system located along the coast of the Big Island. Established in 2000, it is not yet a continuous trail, but can be accessed at several broken segments. It is managed by the National Park Service which receives funds to maintain these trails which traverse ancient Hawaiian sites of cultural and historical significance.
I have hidden 3 caches along my favorite segment which connects Hapuna and Mauna Kea beaches. If you decide to hike the entire trail and collect all three, it's about 1.8 miles round trip and can be accessed from either beach.
Non-residents are asked to pay a $15 entrance/parking fee at Hapuna. To access Mauna Kea beach, you must request a parking pass at the security booth. Non-residents are then charged $21 via credit card at an automated gate.