Most people think of #divewatches as rugged tools. In reality, they’re tiny pressure systems engineered to survive the ocean. At sea level, a watch experiences 1 atmosphere of pressure. But every 10 metres of seawater adds another atmosphere. At 40–50 metres, that’s 5–6 atmospheres pushing inward from every direction. That pressure is relentless. It tries to force water molecules through any microscopic opening in the case. The solution is a system of gaskets at the crown, crystal, and caseback. At the surface, they seal through compression. As depth increases, external pressure forces the gaskets tighter into their seats, strengthening the seal. In other words: the deeper you go, the harder the ocean works to keep the watch sealed. It’s one of the quiet marvels of #watchmaking, and exactly the kind of engineering behind the #Marathon #GSAR. #purposebuilt