Manini Beach is a locals' haven featuring black lava rocks, turquoise water, impressive waves, and a lovely and extensive grassy area with picnic tables shaded by trees.
Get there early and bring your lunch, though remember to pack everything in and out. The beach doesn't have a ton of amenities, but it's a small sacrifice for tranquility.
Bring swim shoes with you, and make sure to bring reef-safe sunscreen like Sun Bum Mineral SPF 30 Sunscreen Spray, which complies with the state's ban on certain chemicals.
Kayaks and standup paddle boards are banned here, but the waves are perfect if you're an experienced surfer. Swimming and snorkeling are also lovely when the water is calm.