This study explored the use of automatic identification system (AIS) data to assess the sheltering effectiveness of three inlet structures in the coastal United States: Columbia River at the border of Oregon and Washington; Freeport, Texas; and the Savannah River at the border of Georgia and South Carolina. Archival AIS data from 212–214 were assembled into distinct vessel transits and partitioned into sheltered and exposed segments. Vessel-performance metrics were defined and compared for the exposed and sheltered segments during high- and low-wave conditions, based on offshore wave information study data. Vessel-performance metrics were statistically analyzed to identify the sheltering effect of the inlet structures. The results show a quantifiable, statistically significant positive impact of jetty sheltering on vessel performance in all three study areas. The procedures developed in this study are intended to quantify jetty functionality from a vessel-performance perspective such that a portfolio of structures may be prioritized for maintenance.