Casio Edifice Suspension ECB-40DB-1A Men's Quartz Watch

What does Water Resistant mean? How to tell if a watch is underwater?

First of all, we want to start by distinguishing the 3 units of measurement of a watch's water resistance;
the waterproofness of a watch is expressed in ATM (Atmospheres), BAR (pressure measurement unit) or Meters.

The waterproofness of watches is generally indicated on the back of the watch, this indication generally refers to ideal and laboratory conditions of water resistance;
for example, when we take a dip in the pool or the sea, less than ideal pressure is applied to the watch,
in the sense that due to various physical laws, the pressure received on the various parts of the watch is much higher than the actual meters of depth at which we find ourselves, therefore we must be very careful when using watches in water, because when If water, whether fresh or salty, enters the inside of the movement (the clock mechanism), damage may be caused which in some cases would be irreparable.

When your watch says that it resists up to 30 or 50 meters... ...it doesn't mean that you can dive up to thirty or fifty meters underwater with the watch.
In reality these figures indicate the barometric resistance of the watch, therefore to be able to carry out diving or for intensive use in water or simply to be able to dive into the sea with the watch,
We recommend using watches with a water resistance rating of at least 100 meters / 10 ATM / 10 BAR or higher.