The purpose of this exploratory qualitative study was to investigate prospective elementary teachers' conceptual understanding of buoyancy. Specifically, the study aimed to identify the scientifically accepted conceptions, and misconceptions that preservice teachers hold about buoyancy using an instructional intervention. Presently, there is a gap in the research literature concerning how preservice teachers understand floating and sinking as it relates to the scientific concept of buoyancy. Conceptions were analyzed using pre/post concept maps, and interviews. Findings showed that preservice teachers had scientifically accepted conceptions and misconceptions about buoyancy as a force and that both conceptions interacted with associated concepts of buoyancy (gravity, weight, mass, density, etc.). Overall, preservice teachers showed a significant deficiency in their content knowledge of buoyancy at the end of the study. Implications include (1) the need for teacher educators to review the science content courses prospective teachers are required to take for certification; and, (2) the need for elementary teachers to understand the concept of buoyancy and all related concepts in order to develop and implement curricula related to the topic of buoyancy.