Not to be confused with patents relating to submarines (in any sense).
A submarine patent is a patent whose issuance and publication are intentionally delayed by the applicant for an artificially long pendency, which can be several years, or a decade.[1][2][3] Analogous to a submarine, submarine patents could remain "under water" for long periods until they "emerged", surprising the relevant market and potential infringers. Persons or companies making use of submarine patents are sometimes referred to as patent pirates.[4][5]
Typically, the submarine patent strategy requires a patent system where patent applications are not automatically published, and the patent term is measured from the grant date rather than the priority or filing date. In the United States, patent applications filed before November 2000 were not published and remained secret until they were granted.
Submarine patents were criticized because they allowed inventors to delay the publication and issuance of their patents, creating uncertainty in the market and enabling them to enforce unexpected claims against competitors long after the technology had been widely adopted.