The town of Marais, Louisiana, is a fictional location. "Marais" is French for "swamp."
Footage of Swamp Thing is used briefly at the end of the Crisis on Infinite Earths crossover on the CW DC shows, it revealed this series took place on Earth 19 of the live action version of the DC multiverse.
Shot in CinemaScope, an unusual format for a television series.
Adrienne Barbeau, who starred as Alice Cable of the 1982 movie version of Swamp Thing (1982), guest stars as a CDC Doctor, Dr. Palomar in Long Walk Home (2019)(#1.8). The Sheriff (Jennifer Beals & her deputy's (mother & son) last name happens to be Cable; the same last name.
The show was canceled before the second episode aired, though it was allowed to complete a shortened season of 10 episodes.