The Return of Swamp Thing t-shirt
I don’t have a manufacturing date for the shirt but based on the movie it’s promoting, I’d say 1989. Daniel Emery Taylor, one of the child actors in the movie, let me know that these shirts were given out to the cast and crew on the film.

I recently acquired the shirt from a vintage clothing store out of California.

The illustration on the shirt is based on artwork by Totleben & Bissette from Saga of the Swamp Thing #34 Rites of Spring
The illustration may look like a close copy of the last page of SotST #34 but notice the feet. The choice to put heels on Abby is quite funny.

Detail: