Hanamaulu Beach is at the edge of a large bay near Lihue shielded from the open ocean where the Hanamaulu stream enters the larger body of water. It forms a lagoon area where fish school for periods of time as they migrate so there's great scuba diving, fishing and sometimes swimming.
The best picnic spot is in the tree-shaded area on the quiet little strip of sand. If you walk upstream from the bay, the wooded banks of the water are particularly fun and camping is allowed with a permit in the 6 ½ acre park.
The beach is off of Kuhio Hwy. (go to Hanamaula Rd., then right onto Hehi Rd.) and there is no lifeguard but restrooms and showers are nearby.