Invasive species pose a significant threat to marine ecosystems, particularly in areas like Chichester Harbour. These invasive organisms can outcompete native species and disrupt local habitats. Scuba divers play a crucial role in monitoring these changes and can help identify invasive species during their dives. Understanding the impact of these aliens in our oceans is essential for the health of marine life and responsible diving practices. Divers should be aware of these issues to help protect underwater environments.