Oceans have absorbed most of the heat from climate change, but they’re now showing severe stress symptoms: heatwaves, loss of marine life, rising sea levels, falling oxygen levels, and acidification. Ocean temperatures have reached record highs, with marine heatwaves doubling in frequency and intensity. Coral reefs, which are highly vulnerable to warming, could lose up to 90% of their species this century. Sea levels are rising at an accelerating pace, threatening millions living near coasts. Acidification weakens marine life, and oxygen loss is also impacting ecosystems. While these changes are inevitable, reducing emissions could slow the damage and buy time for adaptation.