Dark lava rocks rise up from the waters of Honokohau Beach.  They are the remnants of the Aiopio Fishtrap, built by Hawaiians to capture fish.  An opening in the trap to the sea enabled fish to enter, and the walled sections of the trap allowed fish to be stored until needed.  At high tide, fish entered the trap by swimming through the seaward opening or over the submerged walls.  At low tide, the fish were trapped in the enclosure and were easily netted.  Fishtraps differ from fishponds in that the fish are trapped and caught, but not raised.