What I meant by that were boxes highlighted in yellow. These are important, because you'll be using their bounding box. I see that you already have a standing sprite, which is good. You technically don't need the other two (Top-Down Swim and Duck) if you won't use these abilities. Maybe do a Duck for good measure.
You'll find Bounding Box settings under the Custom Sprites category. Platform Builder usually does well to assign these values automatically, but in this case you may need to adjust.