The group was founded in 2021 to highlight the amount of people getting sick when they swam in the river, and now has around 90 members, with 45 citizen scientists.
So far, they have surveyed the River Avon five times this year, with recent surveys showing some E. Coli bacteria, which comes from either raw sewage or agricultural pollution.
Their tests indicate the river meets minimum standards to swim in.
“Our overall mission is to build that picture of of what kind of pollutants are in the water and to demonstrate to the public what power we all have in our hands to make a difference, to make a change,” group member Megan Ruth-Trump told BBC Radio Breistol.
Ms Ruth “married” the river in 2023 as part of efforts to highlight pollution.
She said the puppet will be loosely based on the stories of the goddess Ivona, and will be “beautiful, but also have fangs, as rivers can take away as much as they give”.