I have no idea where this idea of chinampas as floating gardens came from but it’s an enduring myth. Floating gardens using soil are practically impossible - the displacement required to keep enough earth floating for a root system is massive.

The chinampas worked very well because the Aztecs had a large labor force cleaning their latrines into the lake where it would decompose into night soil and later be dredged up to refill the chinampas between growing seasons.

Once they were built up within the underwater stakes, they planted Ahuejote and Ācātzin trees along the edges and corners whose root systems kept the islands from eroding away.