I visited the floating islands on Lake Titicaca near Puno, Peru. The islands are made by cutting sections of the reed roots (which are buoyant) and tying them together. Cut reeds are then placed on top of this base, and the whole thing is anchored to the bottom of the lake (only 3 or 4 metres deep in the part of the lake). They even had floating pig styes.
Each island is small, home to between 5 and 10 families. The families fish, hunt for birds and welcome tourism.