Teaching about water chemistry is important because it connects key science topics, such as chemical reactions, ecosystems, climate change, and human impacts on the environment, that are part of most secondary school curricula. Exploring how the ocean absorbs carbon dioxide and how processes like acidification and eutrophication occur helps students apply core chemistry and biology concepts to real-world challenges. It also encourages critical thinking about global sustainability, environmental stewardship, and the vital role oceans play in supporting life on Earth.