Understanding the difference between water-resistant and waterproof

Water resistance is tested under static pressure: 3 ATM survives splashes, 5 ATM hand-washing and rain, 10 ATM swimming, 20 ATM and up diving. Swimming-pool strokes, hot showers and saunas add dynamic pressure and steam that ratings do not cover.

Rules that protect every watch: screw the crown down, never operate pushers under water, rinse after salt water, and have gaskets checked every two years.