The world's oceans hold a treasure trove of biodiversity and ecological importance, yet much of it remains unseen by human eyes. With the looming specter of climate change, understanding marine ecosystems is more critical than ever. However, observing these underwater worlds presents significant challenges. This is where underwater acoustic monitoring steps in, enabling scientists to listen in on the ocean's soundscape and gain valuable insights into its well-being. In this article, we explore the critical role of underwater acoustic monitoring, focusing on passive acoustic monitoring, digital hydrophones, and acoustic recorders, in driving forward climate change research.