In Bill Grantham’s Creation Myths and Legends of the Creek Indians (University Press of Florida, 2002), he cites John R. Swanton to the effect that various sorts of aquatic creatures are found in Muskogee mythology:
Swanton mentions, with little description, several water beings. Among these are the water bear, water calf, water bison, water tiger, and water person. The last of these, the water person, was described as about four feet tall and having long hair. Also mentioned by Swanton with little description are Wiofû’tc miko (water king deer), which caused certain diseases, and a Spirit of War that appears to have been in human form.