watchOS 5.3.9 (build 16U693) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2021-01-26T18:26:32Z. The update package is 151.55 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: 0b221c1f76c58322436694376075cb252ef2dd7b.zip.