As adjectives the difference between swampy and fenny
is that swampy is describing land that is wet like a swamp while fenny is characteristic of a fen; marshy, swampy.
swampy
English
Adjective
(er)
Describing land that is wet like a swamp.
See also
* marshy
fenny
English
Adjective
(
en adjective)
Characteristic of a fen; marshy, swampy.
Living or growing in a fen (now only of plants).