This study examined high offshore ozone events in Galveston Bay and the Gulf of Mexico, using boat data and WRF–CAMx modeling during the TRACER-AQ 2021 field campaign. On average, high ozone is caused by chemistry due to the regional transport of volatile organic compounds and downwind advection of NO_x from the ship channel. Two case studies show advection of ozone can be another process leading to high ozone, and accurate wind prediction is crucial for air quality forecasting in coastal areas.