watchOS 5.1 (build 16R5589c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-10-22T17:19:35Z. The update package is 748.08 MB. This is a delta (partial) update that requires 4.3.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 45bec3ed21210b593cea5cd302c8ce04442f1970.zip.