If an activity is under way, it has already started. If an activity gets under way, it starts. An investigation is underway to find out how the disaster happened The conference gets under way later today with a debate on the family
A vessel is under way according to the navigating laws, "when she is not at anchor, made fast to the shore or aground " Generally speaking, it means that she is proceeding on a course
the description of a ship as soon as she begins to move under canvas power after her anchor has been raised from the bottom; also written as 'under weigh '