According to a tweet published by 无条件爱国 on December 20, 2023, a video has emerged showing a Chinese PLA Navy Type 039C submarine undergoeing sea trials.

According to information published by the Indian government on December 25, 2023, Indian Navy has taken action following a suspected drone attack on the Liberian-flagged chemical/oil tanker MV Chem Pluto. The vessel, carrying 21 Indian and one Vietnamese crew member, was reported attacked on December 23 and safely reached Mumbai's outer anchorage on December 25.

According to information published by the South Korean MoD on December 22, 2023, the Defense Acquisition Program Administration (DAPA) of South Korea announced a significant step in its naval defense capabilities by signing a contract with Hanwha Ocean. Valued at 1.1 trillion won, the contract is for the construction of the third vessel in the Jang Bogo-III Batch-II submarine series.

According to information published by Суспільне on December 28, 2023, the Security Service of Ukraine (SBU) has incorporated two unmanned surface vessels (USV), Sea Baby and Mamai, into its Black Sea operations. The drone, known for its high speed of up to 110 km/h, has been involved in attacks on Russian naval vessels, including a landing ship Olenegorsky Gornyak and the tanker Sig.

On December 26, 2023, the Indian Navy commissioned the Visakhapatnam-class stealth-guided missile destroyer INS Imphal in Mumbai. This event was presided over by India's Defence Minister Rajnath Singh.

According to information published by the Indian MoD on December 20, 2023, the Ministry of Defence of India finalized a contract, with Mazagon Dockyard Shipbuilders Ltd (MDL), for the procurement of six Next Generation Offshore Patrol Vessels (NGOPVs) for the Indian Coast Guard (ICG). The agreement is valued at ₹1614.89 crore (US$200 Million).

On December 26, 2023, the Russian Ministry of Defense confirmed an incident in the Crimean port of Feodosia, where the Ukrainian Armed Forces targeted the Novocherkassk (BDK-46), a Ropucha-class landing ship of the Russian Navy's Black Sea fleet. This event, confirmed by both Russian and Ukrainian sources, has generated various interpretations, some of which suggest that the ship may have been irreparably damaged.

On December 22, 2023, Austal Limited announced that its American subsidiary, Austal USA, has been awarded a substantial contract by the United States Navy. Valued at US$867.6 million (approximately A$1.28 billion), this contract is for the final design and construction of three Expeditionary Medical Ships (EMS).

On December 22, 2023, the commander of the IRGC Navy, Alireza Tangsiri, stated according to Iranian media that the naval forces of the Islamic Revolutionary Guard Corps (IRGC) now possess Abu Mahdi cruise missiles equipped with artificial intelligence (AI) technology, significantly enhancing their maritime offensive capabilities and allowing them to be remotely guided after launch.

The British Ministry of Defence has confirmed the deployment of HMS Trent, an offshore patrol vessel, for joint exercises scheduled after Christmas. Guyana, a member of the Commonwealth and the only English-speaking country in South America is facing renewed territorial claims by Venezuela over a part of Guyanese territory rich in natural resources.

On December 20, 2023, Boeing officially handed over the first Orca Extra Large Unmanned Undersea Vehicle (XLUUV) to the U.S. Navy. This significant milestone follows the successful completion of the vehicle's acceptance tests earlier in the month. The Orca represents a new breed of the autonomous submarine, designed to carry out extended missions independently.