The highest commercially navigable lake is Lake Titicaca, which lies in the Altiplano at a height of 3,810 m (12,500 ft) above sea level on the Andean border between Peru and Bolivia. Its surface area covers approximately 8,300 km² (3,200 miles²) and has an average depth of between 140-180 m (460-590 ft), i.e. deep enough for the safe passage of commercial vessels. The freshwater lake also sustains an archipelago of over 40 floating islands made entirely from boyant totora reeds, and which are home to the indigenous Uros tribe. These islands fluctuate in size, as the bottom layers of totora rot away and their surfaces are constantly replenished.
The landlocked Bolivian navy regularly practices on it too!