Although the Series 2 Apple Watch is water resistance, the Apple User's Guide states that exposing the watch "to soap or soapy water" while showering or bathing or to "insect repellant lotions, sunscreen, oil, or hair dye" will diminish the water resistance of the watch and "should be avoided." Unless one is accustomed to showering without soap or swimming only in indoor pools, this seems to make the water resistant quality of the watch a none too useful feature.
Watch off before applying insect repellent or sunscreen it ought to be fine. Just be sure and rinse the device in fresh water at the end of the day.