About 7,000 recycled bottles were used to make 10-by-10 foot floating islands.
Tuesday morning, school kids helped place hundreds of plants in them.
The floating gardens were then launched into a community pond where they will be anchored in place.
The islands will provide refuge and nutrition for the local fish.
"The plants that are being put here are water-borne plants; the roots will go down to the water and then the plants will, as they grow, they will take nitrates out of the water and clean up the water quality," Mayor Bob Simmons said.
Walnut Creek is the first Bay Area city to use these floating gardens. If all goes well, they plan to order more to restore the habitat of a nearby lagoon.