The majority of the music was recorded at Estudio Elefante in València, Spain, and made use of Spanish musicians: keyboard/bass player Cris Belda, singer Anna Ferrándiz, the horn section of David Cases and Manu Pardo; and a string quartet.

[9] Writing in Mojo, Kieron Tyler described the album as "a multi-layered rumination which takes a while to beguile," and noting that "the past echoes through the present [and] Down to the Marshes explores this psycho-temporal terrain... Tuareg-style blues, dives into raga-esque extemporisation and English folk-informed balladry are seamlessly woven together.

'The Spirit World' is a fantastic opener with graceful brass and violin, and the title track boasts marvellous avant-folk guitars..."[11] Writing in Silent Radio, Andrew Neal hailed Down to the Marshes as "an absolute delight.. [stirring] together arcane folk, Indian modalities and complex post-Beefheart blues with pop melodicism to create an intoxicating brew.

"[12] Noting that "Callahan does not entirely renounce the tones of someone who can and will 'address the nation'" (and praising his work as arranger as well as performer), Beppe Recchia of Blow Up comments that "variety [is] the album's trump card, and if 'Father Thames and Mother London' rolls a creeping melody between hypnotic guitar riff and controlled Hammond bursts, 'Robin Reliant' rivals Bob Mould's best for its immediate and robust pop-rock but stands out for its astute use of strings and piano; and 'Island State' closes with a chorus of ghostly voices and a guitar filled with Durutti Column reverb... Down to the Marshes is not only David Lance Callahan’s best solo work, but ranks among the peaks of his almost forty year-long career.

Santoni had particular praise for "Father Thames and Mother London", which "bitterly photographs a capital city where visitors are 'queueing gawpers who pay for a cartoon bloody dungeon' and residents don’t really even know who lives next to them," and for "the stunning 'Robin Reliant', which, returning to [Callahan's] second great passion, birdwatching, shows us the talent and state of grace of one of the UK’s most personal and creative artists, capable of creating his own genre with his own rules, moving from his love for sampling and the Krautrock influences of his former band Moonshake to the development of a new English folk.

"[14] Writing from a slightly more avant-garde perspective, Wilder Gonzales Agreda of the Peruvian Avant Garde blog described the record as "a re-birth within more acoustic and folk sounds, in a magical realism mode, than those that won [Callaghan] post-rock fame.

There we can feel a certain indie post-punk affiliation of They Might Be Giants - 'Down to the Marshes', 'Robin Reliant' - and even the throbbing of Tony Conrad and La Monte Young in "The Montgomery", an enigmatic piece in which guitars, keyboards and brief distortions create a precise porridge for Callahan's statements, a bard lost in the accelerationism of the present days...

Don't ever land..."[16] Praising in particular the "deft unfurlingness" and "craft[y] momentum" of "Kiss Chase", the "tricky-yet-hypnotic" feel of "Father Thames and Mother London", the "moodily acerbic, jagged and evocative" atmosphere of "The Montgomery" and the "wistful and forthright" "Island State", Dave Cantrell of Stereo Embers wrote of the album that "one senses the artist's cynicism warming in the sun... Down to the Marshes, in its essence, resonates at its deepest core with the buzz of this brief, often confounding but always curious existence we're blessed with no matter our birthplace or background, echoing throughout with the desires, the drive, the desperate love, all the mess that makes us us, defining along its way the tricky cadence of the human soul.