What does water resistant mean and what is ATM?

Understanding how water resistant watches are can be confusing. This is because some manufacturers provide the figure in feet, some in metres and others in ATM.

So what is ATM? It stands for Atmospheres, which is just a way of describing the amount of pressure put on the watch, when it is at a certain depth of the sea. So for example if your watch says it is water resistant up to 1ATM, this would mean it could withstand the pressure of the (still) water at a depth of 10 metres or 33 feet. This does NOT mean that you can now swim in your watch or take it into the shower, because the force of the water from the shower or swimming exceeds 1ATM. So ATM is a pressure reading not a depth reading. Screw down crowns and screw down backs of watches generally provide more water resistance. Sudden changes in temperature, like going into a hot bath or shower or the cold sea would have an effect on the watch seals and continual use of this kind will probably cause some water to seep in and ruin it. If you need something that’s really waterproof you’re looking for a diving watch that needs to be around 20ATM and above. Here’s a quick usage guide to help you understand the different levels of ATM.1

1 ATM -33 Feet – 10 Metres - Including SPLASHPROOF.  Only protected against accidental contact with water. Will not withstand much water pressure so no washing the dishes or showering with this level, just take it off before you start.

3 ATM – 100 Feet – 30 Metres. Will withstand splashes, a little ‘dunk’ in the water or rain with ease. Not good enough for washing the dishes (phew!), swimming or showering though!

5 ATM – 165 Feet – 50 Metres. Ok, now you’re really talking a cool piece of equipment, can wear it to do the dishes (oh no!). We have seen many watch sellers say that it is suitable for showering and swimming, although we recommend 10ATM. (Ps not ready for bathing or snorkelling yet).

10ATM – 330 Feet – 100 Metres. Whoa, who’s looking good in the bath? You can bath, shower, snorkel and yup you can still do the dishes I’m afraid!

20ATM – 660 Feet – 200 Metres. Will the real James Bond please stand up. You are ready to go recreational sea diving. If you need to go deeper you need a watch certified by the divers watchers international standard to be fit for your depth and type of diving.

Most watches are up to 10ATM and shouldn’t be worn whilst swimming or bathing. You must check if your watch is fit for purpose with a competent professional. This is to be used for guide purposes only.