Very easy. Could be a Walrus, could be a Sea Lion, could be a giant radioactive Slug.

Difficulty : Beginner
Number of Bills : 1
Denomination Recommended : Any
Credits : Origami with Dollar Bills by Duy Nguyen.

Diagram [PDF] (currently none available)

Side
Walrus 01-01
Front Angle
Walrus 01-02
Rear Angle
Walrus 01-03
Top
Walrus 01-04