This popular cave is located on Portugals Algarve coast. You can take a boat there, but it only operates in the middle of the day when the light is harsh and there are plenty of traces in the sand and poeple around. So I took the plunge and swam with my camera protected in a beer cooler through the cold water and had the cave to myself for 2 hours. The high tide had swiped all footprints away, so the only ones you can see are my own.