We quickly dispatch two very small tri-point screws holding a tiny panel to the watch case.

Behind the tiny panel we find a set of contacts that align perfectly with the location of the hidden diagnostic port.

Not wanting to make contact, we quickly dispatch this little connector.

Still unable to remove the diagnostic port door, we resort to pushing it free through the little holes on the inside of the case.

There's got to be an easier way to access the door than disassembling the whole watch—but we're not privy to Apple's secrets.