watchOS 5.3.9 (build 16U693) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2021-01-26T18:26:33Z. The update package is 116.56 MB. This is a delta (partial) update that requires 5.2.1 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: a441498da0ef8c9f1bbee4c69b280af0ddbd349b.zip.