This is a pretty stretch of beach north of Anahola Bay. There isn't really any swimming here due to reefs and rocks, but if you walk south far enough you'll find a place to enter the water and get wet. Be careful of currents. Aliomanu beach is difficult to find, the following google map
shows you the parking area. Driving north on the Highway you'll exit onto the second Aliomanu road (it doesn't connect with the first Aliomanu road exit). Then turn left onto Kalalea View drive, and take the first public road to the right. At the end of the road is parking area for both Aliomanu beach and Papaa Bay..