N-Sea Expands Fleet with Methanol-Ready Cable Maintenance Vessel

Dutch subsea services specialist and vessel operator N-Sea is increasing its fleet capacity with the addition of a newbuild vessel. The Dordrecht-based company has partnered with compatriot Neptune Marine for the construction of a methanol-ready multipurpose cable maintenance vessel.

The new vessel, named Altera, will be built in Poland and then transferred to the Netherlands for fitting and commissioning. The project is expected to be completed in the second quarter of 2026. Altera will be equipped with essential features such as a 25t offshore knuckle boom crane, a mooring system, a 4,500t carousel, a 15t tensioner, and the ability to accommodate up to 99 people.

This expansion of N-Sea’s fleet follows a recent seven-year framework agreement with Italy’s Prysmian for subsea cable maintenance and repairs. The company’s newbuild vessel will be capable of operating year-round in various water conditions, including very shallow and deep waters, for interconnector, export, and inter-array cable projects.

In addition to the Altera, N-Sea has also secured a hybrid survey and ROV support newbuild through a long-term charter deal with Mainport Shipping. This vessel, also being built by Neptune Marine, is scheduled for delivery in the first quarter of 2026.