As per ROR, The word ‘underway’ means that a vessel is not at anchor, or made fast to the shore, or aground. 

The vessel is considered to be at anchor when the vessel's anchor is down and is holding. In any other use of the anchor, vessel is not considered to be at anchor. In all these cases vessel is considered to be Underway.

If the vessel is dragging anchor or if we are using the anchors to turn the vessel, in these cases the vessel is considered to be underway and not at anchor.