There was a brief animated Swamp Thing series around 1992. The series was a tie in to the Kenner Swamp Thing toy line and featured characters based on the action figures. Apparently CBS had an option on the series but was not interested, so only five episodes were made. The shows later aired on FOX on Saturday mornings.More recently, the shows weere rerun on the Disney Cartoon channel.

To here the theme song for the Animated Swamp Thing visit: The Comic Book Resources Site

1 The UN-men Unleashed
Arcanes assistants try and capture Swamp Thing, but end up trapping themselves. Two kids, Delbert and J.T. are warned by Tomahawk, a game warden to avoid Dr. Arcane. Arcane uses his Transducer machine to create mutants to attack Swamp Thing. These UN-men capture Delbert and J.T., who are in turn rescued by Arcane's step daughter Abby. Bayou Jack helps Swamp Thing raid Arcane's lab.
Note: this episode also features a review of the origin of Swamp Thing
 
  2 To Live Forever

3 Falling Red Star

4 Legend of the Lost Cavern

5 Experiment in Terror

 The first episode was released on videotape.