It is not advisable to wear your watch in the shower, even if it is water-resistant.  The high temperature of the water, the surfactants in soap and the pressure of the water as it leaves the shower head are factors that, together, can overcome watch seals designed for diving.

A water-resistant watch may be worn in the pool but the crown must be firmly pushed in or screwed down, depending on the model. 

As far as possible, avoid submerging leather straps in water. They are not suitable for wearing in water and will age rapidly with humidity.