I photographed a couple of them in different habitat types while they were waiting for the tide to recede.
Perched in Coyote Brush (Baccharis pilularis):
Peering out from behind some Pickleweed (Salicornia pacifica) at the very upper edge of the salt marsh:
At the top of the vegetation in a brackish water marsh:
On Bodega Head during the breeding season, Marsh Wrens are typically associated with deeper, freshwater marshes that support dense stands of Bur-reed (Sparganium eurycarpum) and Panicled Bulrush (Scirpus microcarpus). But in winter, their habitat use broadens, and they may also occur in salt marshes — as in the second picture above!
For a little more information about Marsh Wrens, you can review the post from 18 February 2012.