Something Splashing This Way Comes

With apology to William Shakespeare for his "something evil this way comes."
This painting may or may not contain an evil connotation. However these two Natives are taking no chances. The scenario is that they are hearing some sort of activity. The noise-maker is just out of sight and somewhere among the marshland cattails. Could it be an enemy? Might it be an animal of the marsh? The degree of noise might suggest anything from a muskrat, beaver or perhaps even a deer, elk or moose. You may imagine your own conclusion.