Coast Guard Authorization Act of 2023 This bill addresses Coast Guard operations, maritime security, and related matters. The bill authorizes for FY2024 and FY2025 the Coast Guard's active-duty personnel and military training student levels and activities related to information technology, environmental compliance, and other purposes. The bill authorizes the Coast Guard to suspend a license, certificate of registry, or merchant mariner's credential if it has probable cause to believe that an individual poses a threat to others on a vessel. Further, the bill extends existing vessel registry requirements prohibiting foreign ownership to vessels supporting alternate energy production or transmission or commercial space exploration activities over the Outer Continental Shelf. Among other provisions, the bill also requires the Coast Guard to provide ballast water quality data to any state or territory upon request; establishes the felony crime of grossly negligent operation of a vessel when conduct results in serious bodily injury; authorizes the President to direct or control foreign-flag vessels when a cyber incident, transnational organized crime, or foreign state threats endanger U.S. security; and authorizes the Coast Guard to respond to cyber incidents, transnational organized crime, or foreign state threats to prevent damage to structures located on and near navigable waters. The bill also modifies the minimum requirements for various merchant mariner credentials, including by reducing certain service time prerequisites and extending eligibility to noncitizen nationals of the United States. (Generally, individuals who receive U.S. nationality by virtue of being born in, or having parents who were born in, the U.S. outlying possessions are U.S. nationals but not U.S. citizens.)