Most watches are considered water resistant, meaning that they will withstand some splashes or rain. Water resistant does not mean that you should shower or go swimming with the watch on. If you wanted to wear your watch swimming, look for depth resistance.
A watch this is just water resistant is good for everyday wear and is fine in the rain or if it gets splashed but it is not suitable for swimming.
50m water resistance is suitable for water related work, recreational swimming & fishing but not diving or surfing, etc.
100m water resistant watches are suitable for recreational surfing, snorkelling, sailing and other water sports but not diving.
Watches rated for 200m water resistance are suitable for professional marine activities and serious surface water sports but are still not suitable for diving
A divers watch with 200m water resistance is suitable for scuba diving at depths not requiring Helium gas.
A divers watch with 300m water resistance is suitable for deep sea diving at depths that require Helium gas.
Watches should never be worn in shower, spa's or hot pools as the heat and chemicals can cause the gaskets to deteriorate and fail, which in turn will let moisture in to your watch.