Hector and Marta, a friendly local fishing couple, rent out two sweet double rooms and a self-contained house sleeping up to seven. All come with stoves, gas refrigerators and solar-powered outlets for charging phones. Look for the salmon-orange house with the green flag just north of where trucks stop (and the 'Hay Pescado' sign when they've got fish to sell!).
There are plenty of other rooms to rent around Cabo Polonio (ask at El Templao market if you're stuck).