Luckily the International Organization for Standardization (ISO) has developed a standard, ISO 22810, that puts in place a set of minimum requirements a watch must meet to be declared "water resistant." The standard will test the qualities and features of watches and create official labels and nomenclature, as well as explanations for the terminology in order to stay confusion. For a long time, water resistant watches were falsely advertised as "waterproof," a marketing strategy that was put to rest in the 1970s. In 1990 the ISO published ISO 2281, which is what ISO 22810 is now replacing, clarifying any obscurities in language and updating the testing to meet the advancements of technology.
ISO 22810 covers watches intended for daily use and swimming; watches that can be used while scuba diving are covered by ISO 6425.
According to a statement released by ISO, "International Standard ISO 22810 puts onus on manufacturers to prove their watches are water resistant against criteria of industry best practice and international know-how."
So how do you know what sort of watch you should buy? Until ISO 22810 is put completely into effect, use the following guide.
If a watch is labeled as "water resistant," it will resist moisture from light splashing, rain, sweat, etc. If you don't plan on any water-related activities, you should look for at least this basic form of water resistance to be safe.
If a watch is labeled as "water resistant 30M," it will resist moisture and can be submerged for short periods of time. For instance, you could wear the watch while doing dishes, but not while swimming.
If a watch is labeled as "water resistant 50M," it will resist moisture and can be submerged for longer periods of time, while swimming in shallow water, for example.
If a watch is labeled as "water resistant 100M," it can be worn during snorkeling, skindiving and regular swimming.
If a watch is labeled as "water resistant 200M," it can be worn during regular scuba diving.
If a watch is labeled as "water resistant 1000M," it can be worn for deep sea diving.
Now that you know the different depths of water resistance, it should be easier to make an informed choice about what sort of watch you want to buy. Brands like Invicta and Akribos watches offer a number of water resistant watches, ranging all the way up to 1000M.