Sentence:  When a duck <WSD>dabbles</WSD> its bill in mud, it is using the lamellae (transverse plates) on the inner edges of its bill as a highly efficient filter. As the duck <WSD>dabbles</WSD>, its tongue acts as a piston, sucking water or mud into the mouth and driving it out again. Only the edible particles are left behind on the lamellae. 
Meaning of the word marked with <WSD> tags:  To cause splashing by moving a body part like a bill or limb in soft mud, water, etc., often playfully; to play in shallow water; to paddle.