Lürssen's 358-foot O3, once known as Shackleton, heads to billionaire owner after sea trials

A newly delivered 357-foot superyacht is drawing attention online for its immense size.

Now delivered, O3 — the Lürssen yacht once known as Project Shackleton — has begun its time at sea.

The vessel was delivered after departing Lürssen's Hamburg site, pausing briefly in Kristiansand, Norway, before continuing along Denmark's coast, Boat International reported.

O3 has been one of the more secretive yacht projects in recent years. The vessel first changed hands in 2018 through Moran Yacht & Ship under the name Project Icecap and was sold again in 2022 while still under construction.

After that second sale, the yacht was stretched and modified, with one of the biggest changes being a large helideck added to the aft end.

Designed with expedition use in mind, O3 reportedly has an ice-classed hull, cargo capacity, a heli-hangar, space for up to 20 guests, and a total volume of 6,561 gross tons.

On one hand, O3 represents a significant engineering achievement. It uses diesel-electric propulsion and, as Moran previously said, includes energy-saving, power storage, heating, and cooling systems.

Still, a private explorer yacht of this scale comes with a more difficult reality: Even with efficiency features, massive luxury vessels require huge amounts of materials, fuel, and operational support.

That demand carries consequences and can put additional pressure on coastal communities and marine environments already grappling with pollution, rising seas, and strained resources.

Images of floating mansions equipped with helidecks have also become a symbol of unequal consumption.

For now, industry coverage has largely focused on O3's scale and ambition. BOAT International described the vessel as "curated for exploration" and noted that, following delivery, it is now "one of the world's largest explorer yachts."

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