The most important thing about the waterproof of the watch is the sealing ring, or O order, I order, which is made of rubber, nylon or Teflon (Teflon). The joints form a watertight seal. The degree of sealing is the waterproof level. Common labels are: 30M, 50M, 100M, 200M, etc. In addition, the thickness and material of the case are also important factors in determining whether a watch can be safely worn underwater. According to regulations, watches marked with water resistance must reach two air pressures (2 bar). The detection method is: keep the pressure under 2bar for 60 seconds, and the air flow cannot exceed 50 micrograms.

Watch sellers may not label their watches as "completely waterproof". Even if a watch is designed for deep-sea diving, it cannot be claimed to be completely waterproof. That is to say, there is no absolut.