We are on a small outcrop of rock, both behind and in front of us lies the shallow river. We are waiting while the driver pulls the boat over some rocky rapids. In the distance sunlight spills in through the jagged mouth of the cave, illuminating the white and ochre colored walls, and the green of the jungle outside reflected in the surface of the water. A large white rock topped with green sits right in the middle of the opening, the only place exposed to enough light for something to grow.