tessellating gardens are designed to reduce toxic algae in the Charles River, and to filter the water enough that it can be used to irrigate the garden's edible crops. Constructed out of widely available materials including dimensional lumber, each hexagon floats on recycled bottles and 50-gallon drums. To reduce the influx of sediment from the water, the top of each garden is covered with fine gravel and a protective fiber mesh. On one side is a solar-powered rotor that lifts toxic algae onto the garden surface, where it can be eaten by aquatic snails. A metal mesh protects the snails from birds. 

 The garden is designed to address the consequences of high runoff of phosphates into urban waterways; in warm weather, this runoff feeds toxic algae blooms that make the Charles unfit for recreation, especially swimming and fishing. tessellating gardens aims to help all people who take pleasure in a healthy urban river, especially those who would like to use the Charles for active recreation. Although water-gardening has long existed in Asia and Central America, its potential has been neglected in the U.S. tessellating gardens is an innovative step forward in the treatment of urban waterways, using plants and shelled creatures to filter water in a deliberate way, while adding a decorative element to the riverscape that also produces edible food. It is the first time that a floating urban garden has been presented as a practical tool for improving water quality.