Floating like greenish-gold or cerulean blue orbs over bogs, swamps, and marshland at twilight, water sheerie (SHEAR-ree) appear to be small children or pinky-sized faeries with lanterns. Sometimes murmuring a musical mewl, they entice lost or weary travelers to follow them to a warm, well-lit haven in the distance.
But the sheerie never let unsuspecting travelers catch up. Instead, using dark magic, they remain out of reach and lead wayfarers on an endless chase. Hovering above a bog-hole, they force the traveler into a watery grave.
Because of that, these shimmers of light are often called “corpse candles.” Others define the mysterious swirls of light as solitary faeries whose hostility and jealousy drive them to create misery, madness, confusion, and death. Still others believe they are the souls of unborn children trying to return to the mortal world.
Unlike water sheerie who inhabit watery realms, land sheerie are associated with raths, mounds, and barrows—pagan earthworks. There they lure unwary travelers off cliffs or into deep water
Will-o’-the-Wisp
British folklore refers to these phantom flames as “will-o’-the-wisp.” Will is derived from the Saxon word wile, which means trickery or deceitfulness. Wisp, a Swedish word, means a handful of lighted twigs or hay used as a torch.
The lights are named after a mythical figure named Will, a lost soul who has been denied entry to heaven and hell. Thus, he wanders the moors holding a wisp of burning tinder. Like the sheerie, a will-o’-the-wisp flickers over bogs and marshes at night, misleading weary travelers into dangerous swamps. Some legends say the will-o’-the-wisp is mischievous fairy folk guarding hidden treasures.
Regional variations include Spunkies in Scotland, Hinkypunks in Somerset and Devon, and Jenny with the Lantern in Northumberland.
Another soul cursed to wander the bogs is Jack of the Lantern (jack-o’-lantern). The name comes from the Irish legend of Stingy Jack, a trickster whose punishment for trapping the Devil was to wander the Earth eternally with a glowing coal stuffed inside a hollowed-out turnip.
Glowing ‘Round the World
Other parts of the world have their own legends about glowing creatures in the swamp.
Snake-like will-o’-the-wisps appear as “firedrake” in European folklore. For centuries, sailors have shared tales of glowing seas and phantom wakes that were tied to sirens, sea monsters, and elusive demons.
In Japanese folklore, balls of fire that float in the air at night are hitodama, souls of the dead that have separated from their bodies. In other parts of Asia, they are the souls of lost fishermen. In Brazil and elsewhere in South America, the luminous lights are the eyes of the great evil serpent Boitatá, a mythical fire snake that guards against humans setting fire to fields and forests.
In Louisiana Creole folklore, the feu follet, or fifollet (foo fow-lay) translates to “marsh fire” or “crazy fire.” Like the sheerie, it tricks travelers into leaving safe paths and drowning. According to some legends, the feu follet were the spirits of deceased loved ones coming back to bid their final goodbyes. In other legends, however, these glowing balls of light were said to be evil entities laying a trap for those unlucky enough to stumble upon them. Parents would tell their children to never follow the feu follet, warning them that it was a demon or monster trying to lure them to their early death.
Reports of sheerie, will-o’-the-wisps, and similar sightings have grown less frequent, a fact attributed to the number of bogs and marshes that have been drained. The sheerie, however, tends to be most active during Samhain and Beltaine, when the veil between the worlds is thinnest.
Scientific Explanations
Scientific explanations range from fireflies and the reflection of moonlight in the eyes of owls to bioluminescent fungi, like honey fungus, and static electricity. St. Elmo’s fire is a bright, glowing blue or violet light that appears like a flame on tall, sharp objects—such as ship masts, airplane wingtips, or church spires—during storms.
But swamp gas is the usual explanation for the phosphorescent balls of light. Attributed to the natural phenomenon of ignis fatuus (foolish fire), it is the result of the spontaneous combustion of methane and phosphine produced by decaying organic matter. But many doubt this explanation since the phenomenon is difficult, if not impossible, to replicate.
According to ZME Science, chemists at Stanford University in 2025 solved the ancient mystery by successfully recreating the ghost lights under controlled laboratory conditions. After introducing microbubbles of methane and air into water, the bubbles accumulated an electric charge at the gas-liquid interface and generated tiny, spontaneous electrical discharges. The resulting microlightning created the signature cool, glowing blue-white flame without heavy smoke.
Literature and Pop Culture
In literature, the will-o’-the-wisp often represents a goal or hope that is impossible to reach.
In Jules Verne’s The Child of the Cavern (1877), mysterious lights, known as Fire-Maidens, appear throughout the novel. In The Lord of the Rings, Frodo and Sam see will-o’-the-wisps while they are travelling through the Dead Marshes. When Sam asks Gollum what they are, Gollum says, “The tricksy lights. Candles of corpses, yes, yes.” And in Bram Stoker’s Dracula, the lights are explained as treasure markers.
In Dungeons & Dragons, the will-o’-the-wisp is a malicious undead creature of pure energy that feeds on the fear and life force of dying creatures. In Pokémon, it is a fire-type status move that inflicts a burn on the opposing target.
In Will O’ The Wisp ~ What Really Are They? The Jolly Reiver offers a folkloric overview of the strange atmospheric ghostly lights that can be found in swamps and marshlands worldwide.
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