<![CDATA[The International Regulations for Preventing Collisions at Sea govern every navigational encounter between vessels, yet the quality of deck officers' procedural knowledge and decision-making competency in applying these regulations under the dynamic, time-pressured conditions of close-quarters situations represents a critical and empirically underexamined dimension of maritime navigational safety. This study investigates the quality and consistency of COLREGs application competency among Indonesian deck officers through a qualitative design combining scenario-based knowledge assessment vignettes with structured interviews and focus group discussion. Data were collected between April 2025 and April 2026 from twenty-four participants comprising active deck officers serving as chief mates and second officers, STIP Jakarta Nautika lecturers, and maritime casualty investigation specialists. Thematic analysis, cross-group comparison, and narrative synthesis were applied. Findings reveal systematic and consistent COLREGs application errors concentrated in three domains: Rule 8 (Action to Avoid Collision) temporal decision-making, Rule 17 (Action by Stand-On Vessel) uncertainty management, and Rule 19 (Restricted Visibility) procedural sequence execution. A convergent expert-officer perception gap regarding the adequacy of current COLREG-focused simulation training provides the study's most practically significant cross-group finding. The study contributes a domain-specific diagnostic of COLREGs application competency gaps among Indonesian deck officers and provides institutionally actionable recommendations for Nautika curriculum enhancement at STIP Jakarta.]]>
