[This paper is part of the Focused Collection on Instructional labs: Improving traditions and new directions.] This manuscript presents a case study of an introductory physics student who, during the remote learning conditions imposed during the COVID-19 pandemic, found inspiration within a new, open-inquiry, project-based, laboratory curriculum designed at Portland State University. The phenomenon investigated by the study subject was intriguing to both the student and the lab instructors for its unfamiliar and instructive optical effect: a ring-shaped pattern or halo created by a laser diffusely reflected in a shallow body of water. Drawing on classwork and interview responses, this study shows that the subject achieved many expected curriculum outcomes, particularly with respect to experimental design and data analysis tasks, indicating that the course's open-inquiry structure can be effective while offering students a free choice of what to investigate in a laboratory class. Additionally, the case study shows that the halo phenomenon is pedagogically rich as it combines refraction, diffuse reflection, and total internal reflection in a nontrivial way, thereby answering calls by physics education researchers for more complex, realistic examples in geometric optics instruction. Finally, this case also highlights challenges students may experience interpreting diffuse reflection and determining the position of optical features beyond image formation, not commonly a focus of introductory physics courses, textbooks, and education research.