This chapter explores when shipmaster conduct triggers Flag State responsibility. While individual acts are not attributable to States, exceptions arise from special State-individual relationships. Influenced by the shipmaster’s traditional role as agent and navigator, the modern role includes a range of internationally codified duties. If stemming from Flag State obligations, the shipmaster fulfills them, supported by two ARSIWA exceptions to non-attributability: (1) when individuals act under State control; (2) when the State fails to prevent conduct. Flag State responsibility for shipmasters’ conduct evolves in rescue violations. It arises when States fail to ensure shipmasters assist persons in distress where reasonably possible without endangering lives onboard, or when rescued persons face treatment violating international refugee law, including human rights law. This chapter re-assesses Flag State responsibility by examining whether shipmasters’ conduct is attributable based on their humanity or presence onboard. It also evaluates when private conduct is attributable to the Flag State, based on (1) organ/agent status under ARSIWA and (2) the State’s due diligence in preventing unlawful acts. Attributability depends on vessel ownership, breached obligations, and the State’s role in prevention. The chapter expands ARSIWA attribution analysis to autonomous ship operations, where shipmasters are absent or replaced by decision-making artificial intelligence.