When serving aboard ship during a 'Cadet Cruise' Cadets are referred to as 'Midshipmen' or 'Middies' and hold authority equal to a WO-1, whatever Branch of Service they may major in.

Liasion Corps, Starfleet Marine Corps, Starfleet Starfighter Corps and Starfleet Officer Cadets all attend the Starfleet Academy or one of its campuses throughout the Federation, taking their "Cadet Cruise" during the Summer months prior to their Fourth Year, with its career specific courses.

During the actual cruise assignment, they are usually referred to as 'Acting Ensign' or 'Acting Third Lieutenant' since they are technically not an 'official' Officer yet, despite having taken their oaths during the Academy Induction.