The aim of this book is to explore how fluids in motion (e.g., waves produced by a hurricane) interact with and exert loads upon fixed and floating structures to ultimately inform their structural design. As such, we must first introduce the study of fluid dynamics to become familiar with the underlying physics that govern natural phenomena such as the propagation of surface gravity waves. This chapter introduces the fundamentals of fluid dynamics at its most conceptual level, before summarizing some important mathematical concepts that are required to engage with many of the derivations presented throughout this text.