XT (Christmas Tree) Installation Vessel

A subsea construction or installation support vessel rigged to lower and land Christmas trees (XTs) onto subsea wellheads and connect them to the field. It carries a heave-compensated crane or tower, a moonpool or over-the-side deployment, ROVs for landing and lock-down, and dynamic positioning to hold station over the well. The same class of vessel installs manifolds, jumpers, and umbilicals. The XT itself follows API Spec 17D; the vessel is a DP construction unit, not a drilling rig.