The Ulstein X-bow [1] is an inverted ship's bow designed by Ulstein Group to improve handling in rough sea, and to lower fuel consumption by causing less hydrodynamic drag.[2] It is shaped somewhat like a submarine's bow.
As of 2010, 15 X-Bow vessels of different types are operating.[3]
The Bourbon Orca, design AX104 is an Ulstein A-Series Anchor Handling Tug Supply vessel, built for Bourbon Offshore Norway, and was the first ship built with the Ulstein X-bow[4] in 2006. The operator claims that the design achieves higher speed and a calmer motion in rough seas.[5]