Removing Activation Lock on Apple Watch Series 3

You cannot use that Apple Watch. Activation Lock prevents other people from using a lost or stolen  Watch.

Only the original owner can remove the Activation Lock. Apple will not help you remove the Lock.

No one here can help you remove the Lock.

Recycle the watch or turn it in to the local authorities, police, sheriff, etc.

M1 Mac mini, macOS 15.2;  Watch, series 10 GPS-only, watchOS 11.2; iPhone 16, iOS 18.2; TV 4th Gen, tvOS 18.2; HomePods, audioOS 18.2 and Airport Express w/ Airplay 2

Turn the Apple Watch in to the local authorities or the

Lost and Found for the location where you discovered it.

Activation Lock is a security feature and there is no

workaround.

If the watch is charged, ask it who owns it 'Siri who

owns this watch'. You might get some information to

return the watch to its owner.

Without the Apple Accound and password used

to initiate the Activation Lock, the Apple Watch

is and will remain useless to you.

It doesn't belong to you. Turn it over to the authorities. While you're at it, google "theft by finding".