The Mahaulepu Heritage Trail is the best antidote to Poipu's resort polish. It follows the dry south-shore coast east from Shipwreck Beach, passing lithified dunes, low cliffs, tide-sculpted rock, and long views over water that shifts from turquoise to deep blue.
There is little shade and few formal signs, so treat it like a real walk rather than a beach stroll. Wear shoes, start early, and turn around before the heat makes the return feel twice as long.