Coastal and marine ecosystems encompass the diverse array of life and physical environments found at the interface of land and sea and extending into the open oceans. These systems, which range from highly productive estuaries, mangrove forests, and coral reefs to the vast pelagic zones and deep-sea vents, are characterized by unique conditions of salinity, pressure, and light that shape the adaptations of their inhabitants. As the foundation for global biodiversity, they support complex food webs, from microscopic plankton to large marine vertebrates, and play a critical role in regulating global climate, cycling nutrients, and protecting shorelines. The immense ecological and economic value of these ecosystems underscores the urgent need for conservation efforts to mitigate threats such as pollution, overfishing, and climate change.