Lake Themistitan is in Mexico. In it is said to dwell the Hoga. This creature is reputed to look like a pig, with tusks which are better avoided. It is supposed to be able to vary its color, assuming hues of red, green or yellow.
Frankly, I am a little dubious about this supposed chameleon of the waters, because these colors do not lend themselves to camouflage. However, I keep an open mind.