Sport clusters are geographical concentrations of private, public, and nonprofit organizations in a denominated area with a shared interest in one or similar sports. This paper addresses the question: How does socioeconomic proximity—linkages between organizations or individuals, which go beyond spatial proximity—influence the development and properties of sport clusters? This qualitative study investigates four sport clusters in surfing and sailing. The findings indicate two types of sport clusters based on different forms of socioeconomic proximity. The surfing clusters are characterized by cognitive proximity based on convergent perceptions and managerial practices. The sailing clusters are characterized by organizational proximity based on complementarity. This article (a) discusses the resilience properties of these two types of clusters and (b) proposes a two-step model of cluster development. Cluster policy makers can draw on this research to consider how to engage early with emerging clusters and foster them by facilitating collective dynamics and projects first and collaborative projects second. Cluster members learn about the long-term value of being involved in clusters and how they can take advantage of cluster involvement.