watchOS 5.3.9 (build 16U693) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2020-11-05T18:19:38Z. The update package is 66.56 MB. This is a delta (partial) update that requires 5.3.5 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 67e3256b84cd788195b7f8eb5a59bcaacb835928.zip.