People don't come to MacKenzie State Park for the swimming, it's mostly the scenery and fishing visitors are after. This portion of Puna's coast is jagged lava fingers and leaning palms. The ocean often punishes these low cliffs, so steer clear of the edge. There is a picnic area perfect for a nice lunch. However there is no potable water. This area does not have the best reputation, so be wary of shady types. Camping is allowed with permit, but not advisable.
In the parking lot is a sign indicating a portion of the King's Highway. It was built by order of King Kamehameha and later repaired by convicts in 1850. Just north of the parking area are some old lava tubes which might be worth exploring. Wear sturdy shoes and bring a flashlight. To get to Mackenzie take Highway 130 south from Pahoa. When it dead ends at Highway 137, turn right. Highway 137 meets and turns into Pahoiki Road for 2 miles. Then Highway 137 turns off to the left. Follow the highway. The park will be on the left after mile marker 137.