Water Monster reports in Colorado
1 case, best-documented first. Page 1 of 1.
We map claims, not creatures. A case is what some source says someone saw or heard, with the link to that source. It is not proof that anything was there, and a retelling counts once, not as a second sighting.

Water Monster · Larimer County, Colorado · 1884
Witnesses report seeing a large, dark, eel-like water monster with a seal-like head in the St. Vrain stream.