A wave breaker, also known as a seawall, is a structural feature built in the sea to protect ports and beaches from the impact of waves and marine storms. This structure plays a vital role in reducing coastal erosion by mitigating the energy of incoming waves, thus safeguarding coastlines. Additionally, wave breakers create a calm marine environment within ports, facilitating navigation and vessel traffic. They enhance the area’s appeal to tourists by creating suitable zones for swimming and other marine activities. However, the construction of wave breakers can lead to negative impacts, including increased erosion in neighboring areas due to altered wave patterns and currents. It may also cause sand and sediment accumulation in specific zones, hindering navigation and contributing to the formation of new beaches. Furthermore, the presence of wave breakers can affect natural marine environments and the organisms that depend on these areas. In this context, we examine the wave breaker located in the oil port of Mohammedia, Morocco, which was built as part of the port’s expansion and spans 1800 m into the sea. We will assess its impact on the city’s coastline and the surrounding marine environment, noting observed negative effects such as changes in wave dynamics and impacts on sand transport and distribution along the shore. Consequently, detailed environmental and engineering studies are essential to evaluate the potential impacts of wave breaker construction and implement necessary measures to mitigate negative effects while preserving ecological balance in the region.