watchOS 5.3.9 (build 16U693) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2020-11-05T18:19:39Z. The update package is 72.18 MB. This is a delta (partial) update that requires 5.3 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: d28c371cbe830d8dc73a3ec7d2a9a234b256ed32.zip.