A vessel and method to perform subsea wellbore related operations, e.g. slim hole technique drilling of a subsea wellbore are disclosed. The vessel has a hull with at least one moonpool defining first and second moonpool areas. A vertical tower is mounted on a tower supporting hull structure and has a vertical operative face. A hoisting device has a winch and winch driven cable, and is adapted to suspend a load from said vertical tower via said at least one winch driven cable and to manipulate the suspended load in a firing line of the tower that extends along and outside of said vertical operative face of the tower. The tower is slewable about a vertical slew axis by means of a slewing drive at least into first and second operative positions wherein the firing line extends through the first and second moonpool areas respectively.