The Sea Shadow was developed in great secrecy, and while it may have been a "stealth ship" it wasn't in fact invisible to the naked eye.

The Navy test craft Sea Shadow in the Sea and Air Parade during Fleet Week San Diego, October 1, 2005.
US Navy/PM3 Sally Mendez

Developed in secrecy in...

https://www.businessinsider.com/why-us-navy-attempt-to-build-stealth-warship-didnt-work-2021-5

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