Hello. The organism have you found is called a rat-tailed maggot. It is the immature stage of a Drone Fly. In their adult form, these flies look similar to honeybees and they are beneficial pollinators. Like all flies, they breed in stagnant water. The "tail" part is their breathing tube. You can read more about them in this article from the University of Florida. https://edis.ifas.ufl.edu/in809

Christa