Simple:
* The birds nested in the marsh.
* We took a boat ride through the marsh.
* The marsh was full of reeds and cattails.
Descriptive:
* The sun setting over the marsh created a breathtaking display of color.
* The air hung heavy with the scent of salt and decay in the vast marsh.
* The marsh, a haven for wildlife, teemed with life.
Figurative:
* The political debate was a marsh of conflicting ideas.
* Her mind felt like a marsh, filled with confusion and uncertainty.
Specific:
* The marsh is an important habitat for endangered species.
* The marsh is being threatened by pollution and development.
* The marsh is home to a variety of unique plants and animals.
The best way to use "marsh" depends on the context of your sentence.