The novel chronicles the lives of the members of the Bigtree family, a clan of ‘gator wrestlers that own and operate “Swamplandia!” a fictional alligator farm cum theme park located in Florida. The story opens on a rather tragic note with the Bigtree family in the midst of suffering all manner of troubles: their clan head, Sawtooth Bigtree, has been fighting a loosing battle with dementia and must now live on a floating nursing home while Hilola, his daughter-in-law, has succumbed to cancer. Her husband and three teenage children survive her. Financially, the family is in bad shape as well as the park has been having difficulty competing with The World of Darkness, a brand new theme park that has opened up nearby drawing away many of their potential visitors.
Hilola’s widower, who the rest of the family simply calls “The Chief,” hatches a scheme to upgrade the park to enable it to compete with The World of Darkness. This plan is met with resistance and skepticism though, especially from his son, Kiwi, who believes that the best course of action would be to cut their losses by liquidating what they can of Swamplandia! The Chief staunchly resists this suggestion saying that it would be tantamount to forsaking their clan’s legacy.
Meanwhile, more trouble brews within the Bigtree family: Osceola, middle child of the family, has developed an unhealthy obsession with the occult having picked up an old book entitled “The Spiritist’s Telegraph.” Her obsession was born from her desire to communicate with her deceased mother. Osceola, together with her younger sister, Ava begin holding necromantic rituals. These séances however are unsuccessful in contacting her mother’s soul. The isolation of the park and her frustration at her inability to reach her mother’s spirit however drives her to reach out and talk to other spirits who are more willing to get in touch with the living. This worries Ava to no end, believing that other spirits might try to possess her older sister.
The relationship between The Chief and Kiwi fare no better as the two continue to butt heads. The two reach an impasse and Kiwi decides to leave Swamplandia to figure out a way to save the park. He manages to land a job as a janitor, ironically at the rival theme park The World of Darkness. Although intelligent and well read, the seclusion of being in Swamplandia nearly all his life makes it difficult for Kiwi to blend in with the rest of his peers. Luckily, a colleague named Vijay befriends him and patiently teaches him the local language and gestures of the local Florida teens. In addition to this he also attends night school. His hard work pays off and he is eventually promoted to lifeguard.
His skills as a lifeguard are soon tested and he saves a young woman from drowning, turning him into a local celebrity. The park management recognizes his skill and bravery and sponsors his training to become an airplane pilot. Things take a turn for the worse in Swamplandia though, pushing The Chief to take drastic action and close the park down. He also mysteriously announces that he will be going on a “business trip”---without stating the rationale or extent of said trip---to the more urbanized parts of Florida, leaving the two younger Bigtrees to manage park affairs in his absence.
While going about their duties the two young ladies discover a derelict boat as they clear foliage on a secluded portion of the island. In the boat they manage to scavenge some memorabilia but more importantly they also manage to literally dig up the dead: using her Ouija board she contacts the ghost of a man named Louis Thanksgiving. He lived during the 1930’s and ran away from his abusive foster family. Being the only male that Osceola has seen in awhile, she falls in love with the ghost and run off together, boat and all, leaving poor Ava alone.
Ava, now on a solitary quest to find her sister, eventually runs into a shady character: a pole boat operator that goes by the name “The Bird Man.” Together, they travel into the deep swamps to find Osceola, voyaging to get to the supposed “underworld” to retrieve her wayward sister. It soon becomes evident that the Bird Man is no mystic as he had claimed to be and that he is clearly up to no good. Ava’s fears are confirmed when she tries calling out for help from a bunch of drunken fishermen and she is quickly muzzled by the Bird Man, who then proceeds to violate her. She manages to escape him though by plunging into the swamp where she is attacked by alligators. Being a member of the Bigtree clan, she manages to conquer the reptile but the fight exhausts her and she is still a long way from home.
The novel then shifts focus back on Kiwi, still in the process of training to be a pilot. He learns that his father, the once proud and autonomous Chief, has been working at a nearby casino for some time now, trying desperately to scrounge up enough funds to salvage his beloved Swamplandia. Upon completion of his training Kiwi’s maiden flight is greeted by the strange sight of his sister Osceola garbed in what looks to be the tattered vestiges of Hilola’s wedding gown. She has been stranded in the swamp for a long time. She narrates that she did elope with the ghost of Louis but was abandoned during their alleged wedding ceremony. Eventually the two come upon Ava and the Bigtree family is finally reunited. Together, they must face the bitter reality that they can no longer maintain Swamplandia. They must move to the more urbanized parts of Florida to integrate into mainstream society.
