Foundations and applications of fluid mechanics are relevant in several scientific and technical fields, like physics, engineering, medicine, environmental sciences, and mathematics. The study of fluid mechanics is included in several school curricula worldwide, and as early as the 1980s, there has been growing interest in the Physics Education Research (PER) field about the subject. Several PER researchers have tried to understand how students' conceptions of liquids or gases can affect the effectiveness of instruction, and many literature pieces are available that discuss different possible ways of teaching the concepts related to the equilibrium of fluids and hydrodynamics. They mainly aim to shed light on how to facilitate student learning of fluid mechanics foundations and applications and foster student broad awareness of how this subject plays a role in so many different disciplines. In this chapter, we discuss some relevant examples of these publications to understand how educational research has contributed to the knowledge of teaching/learning of fluid mechanics, how it has evolved in terms of analysis of student learning in this subject, and methodologies and tools proposed and trialed.