Offshore - Oil & Gas

Sea1 Offshore Launches First OESV Sea1 Diamond

Sea1 Offshore has launched Sea1 Diamond, the first of four 120 m Offshore Energy Support Vessels being built by COSCO Shipping for delivery from 2027.

Photo source: Sea1 Offshore via LinkedIn

22, July 2026
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Sea1 Offshore has launched Sea1 Diamond, the first of four Offshore Energy Support Vessels being built by COSCO Shipping in China.

The vessel entered the water on 21 July 2026 and will now proceed towards delivery. Construction began in September 2025, while work on the second vessel in the series, Sea1 Citrine, started in December 2025.

Sea1 Offshore ordered the first two vessels from COSCO Shipping in November 2024 and announced contracts for two further units in March 2025. The four-vessel series is scheduled for delivery during 2027 and the first half of 2028.

Built to the ST-245 design, each 120 m vessel will accommodate up to 120 personnel. The specification includes a 1,400-square-metre cargo deck, a 250 t deck crane, two ROV hangars and a moonpool.

The vessels will be methanol-ready, and their generators will be capable of operating on 100% biofuel. Kongsberg Maritime will supply equipment packages for the newbuilds, which are intended for operations in the oil and gas and renewable energy sectors.

Photo source: Sea1 Offshore via LinkedIn

Tags: China, COSCO Shipping, OESV, Offshore Energy Support Vessel, offshore vessel, Sea1 Citrine, Sea1 Diamond, Sea1 Offshore, Shipbuilding, ST-245

Editorial Note:
This article was prepared with the assistance of AI tools to enhance clarity and efficiency.
All information has been reviewed and verified by the HMT News editor.

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