I have no information about the Apple ID used in this watch

 contact Apple ID Support. Have a copy of the death certificate and a copy of the will or a document that shows you inherited it.

How to request access to a deceased family member's Apple accounts - Apple Support.

Apple ID - Official Apple Support.    

Contact Apple for help with Apple ID account security - Apple Support.  (Link doesn’t always load)   

Get Support      Work through the screens to get a chat option. 

https://twitter.com/AppleSupport

See About Activation Lock on your Apple Watch https://support.apple.com/en-us/HT205009

See what Eric said above: How to request access to a deceased family member's Apple accounts - Apple Support. If you can't turn the activation lock off and want to make it functional, you will need a court order instructing Apple to assist in the provision of access to a decedent’s information from the deceased person's accounts (from the link Eric posted).

If you have such an order , see these support option for help:

Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362

Apple ID Support https://support.apple.com/apple-id

Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169

Get Support: We’re here to help  https://getsupport.apple.com/. Go through the options to find the best support option.

Eric I apologize for my post. I didn't realize all that your post said. It was too late when I realized that I needed to try to modify mine more acceptably. I kept trying to fix it, but ran out of time.