Blue Dilly, also known as the Blue-Dillon Monster, is a legendary creature said to inhabit Dillon Reservoir in Summit County, Colorado. Often dismissed as a local myth or modern fairy tale, stories of the creature have persisted since the creation of the reservoir in 1962, and it has gained a loyal following of believers, folklorists, and amateur researchers.[1]
Origins and Sightings[]
The legend of Blue Dilly began after the completion of the Dillon Dam, when locals and visitors began reporting strange disturbances in the lake's water. Swells without wind, sudden currents, and sightings of a large, gray, aquatic figure beneath the surface began to circulate, especially among nighttime kayakers and fishermen.

One of the most well-known accounts comes from a couple who, while kayaking back from a small island in Frisco Bay, experienced powerful unseen forces pushing their boats forward through the water. The wife later claimed to have seen a wide, gray creature with a fin and what appeared to be a clawed hand beneath her kayak. She sketched the figure, and her husband became obsessed with uncovering the truth behind the creature, eventually documenting his findings in a self-published book.[2]
Description[]

A colored version of Blue Dilly
Blue Dilly is typically described as a grayish blue, flat-bodied aquatic creature, with a large fin or flipper, and sometimes a vaguely humanoid hand or claw. Witnesses often report sudden propulsion through the water, unexplained wakes, or disturbances near the surface. Unlike traditional lake monsters, Blue Dilly is not always seen, but is often felt — a feature that contributes to its eerie reputation.