U.S. Forces Board Iranian-Flagged Tanker in Gulf of Oman
U.S. forces reported boarding an Iranian-flagged product tanker in a brief operation on Wednesday, May 20. According to The Maritime Executive, the vessel was inspected, released, and ordered to change its course.
The Celestial Sea, a vessel of 11,479 deadweight tons, was suspected of trying to breach the U.S. blockade. Its Automatic Identification System showed Khor Fakkan in the UAE as the destination, but U.S. authorities believed it was headed toward Iran. Marines from the 31st Marine Expeditionary Unit boarded the tanker via helicopter while it was in the Gulf of Oman. CENTCOM reported that the ship was searched and then released.
Details of the Interdiction
U.S. Central Command stated that the tanker Celestial Sea, a vessel of 11,479 deadweight tons, was suspected of trying to breach the U.S. blockade. Its Automatic Identification System showed Khor Fakkan in the UAE as the destination, but U.S. authorities believed it was headed toward Iran. Marines from the 31st Marine Expeditionary Unit boarded the tanker via helicopter while it was in the Gulf of Oman. CENTCOM reported that the ship was searched and then released.
The Celestial Sea is known as part of Iran’s shadow fleet. The United States imposed sanctions on the tanker in April 2025, when it was operating under the name Harmony. The NGO United Against Nuclear Iran reported blacklisting the vessel in 2023. The handysize tanker is reportedly managed from the UAE and has been flying the Iranian flag since December 2025. Before that, Equasis records show it under a false flag from Aruba, and previously flagged in Barbados and the Cook Islands.
Broader Blockade Operations
With this latest action, CENTCOM reported redirecting 91 commercial ships to ensure compliance with the blockade. That number increased by two from the previous day, and was up from 84 on May 18. The U.S. Treasury also announced that it added 19 more tankers to its sanctions list on Tuesday. Separately, neither the Pentagon nor U.S. military commanders have confirmed reports of a U.S. seizure of a stateless tanker linked to Iran on May 19 in the Indian Ocean. The Wall Street Journal reported that the Skywave tanker was intercepted west of the Malacca Strait. That vessel had left the Persian Gulf before the blockade, carrying Iranian crude, and indicated it was offloading in China, though speculation arose about a ship-to-ship transfer at sea.
Strategic Context
These efforts are part of a broader economic campaign by the administration of the current President of the United States, Donald Trump, aimed at cutting off Iran’s revenue to push for a negotiated settlement.
Original Article: U.S. Marines Board Iranian Tanker Celestial Sea Near Gulf of Oman on May 20, 2026 — Indexbox