This paper examines the relationship between development and conservation in South Korea from the mid-1960s to the late 1970s through the case of hard clam (baekhap) aquaculture. While the Park Chung Hee era is often characterized by “destructive development” that entailed environmental degradation, this study shows that some projects, such as the designation of “protected waters,” sought to manage nature in the pursuit of sustainable economic gains. Following the 1965 fisheries agreement with Japan, a sudden export boom in baekhap led the government to promote aquaculture as a major national initiative. Because artificial propagation was not yet possible, natural seed clam grounds were designated as “protected waters” to secure a stable supply. By the mid-1970s, however, the industry faced severe crises due to marine pollution from expanding coastal industrial complexes and the nationwide mass die-off of 1975. After the collapse of baekhap farming, coastal areas once designated as protected waters were reimagined as sites for large-scale reclamation projects. This study argues that the era’s nature-conserving measures were ultimately temporary and palliative, and it underscores the varied experiences of the fishers involved, suggesting the need to expand research on the intertwined relationship between conservation and development by attending to the perspective.