Eterna created a miniature version of a shaft seal, the hollow, doughnut-shaped collar around each shaft in a car's transmission. In a car, the seal prevents high-pressure oil from leaking out. In the KonTiki, it keeps high-pressure water from seeping in. As water pushes on it, the hollow tube flattens out to hug the stem more closely, forming a tighter seal as pressure builds. That makes it more effective at great depths than the O-ring seals in other watches. So it will keep on ticking, and so will you.