watchOS 5.3.9 (build 16U693) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2021-01-26T18:26:19Z. The update package is 173.79 MB. This is a delta (partial) update that requires 5.2 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 0c74fb554999911c0865d865d5ac8358da87942a.zip.