A discussion of the behaviour of fluids, including an overview of the concepts of fluid pressure and Pascal’s Principle. I also discuss Archimedes’ principle of buoyancy and its application to why objects float, and Bernoulli’s Principle of the relationship between fluid speed and pressure, and how this can be applied (and misapplied) to explaining how aeroplanes fly. Recommended prerequisites: Episode 13 Newtonian Mechanics, Episode 27 Intermolecular Bonds and Phase Transitions.