Detailed investigations of student reasoning show that students approach the topic of wave physics using both event-like and object-like descriptions of wave pulses, but primarily focus on object properties in their reasoning. Student responses to interview and written questions are analysed using diSessa and Sherin's coordination class model which suggests that student use of specific reasoning resources is guided by possibly unconscious cues (diSessa and Sherin, International Journal of Science Education, 1998, 20, 1155-1191). Here, the term reasoning resources is used in a general fashion to describe any of the smaller grain size models of reasoning (p-prims, facets of knowledge, intuitive rules, etc.) rather than theoretically ambiguous (mis)conceptions. Student applications of reasoning resources, including one previously undocumented, are described. Though the coordination class model is extremely helpful in organizing the research data, problematic aspects of the model are also discussed.