Hiding out on the outer rim, we find a complex cable assembly—home to the microphone and speaker.

And in between the two, the mystery of the second microphone port is solved. A flexible rubber plug looks like a barometric vent, designed to allow outside pressure to be felt by the internal barometer through the waterproof shell.

The Apple Watch Series 2 is trying to make a splash while keeping dry. This requires no shortage of gaskets and o-rings.

How well do these gaskets and o-rings keep water out? The Apple Watch Series 2 resists water intrusion to a depth of 50 meters, under ISO standard 22810:2010. This means it will be fine in a pool, but may fail during certain activities.