In Pressure, the islanders work together to retrieve a wedding ring that has fallen down a sink drain. With the help of a visiting inventor, they discover what a straw, plunger, vacuum and jackhammer all have in common: They are all useful tools that operate by manipulating a force called pressure. The islanders discover the differences and similarities between devices that derive their power from changing air pressure (pneumatic machines) and from liquid pressure (hydraulic machines). Thankfully, by applying what they learn about pressure and how their various tools work, the islanders recover the missing ring!