Single Occupancy
Offered by only a few cruise lines, most notably Fred Olsen and Costa Cruises. Single cabins are specifically designated to be occupied by one person and may help you avoid the single supplement.
Other cruise lines do set aside a limited number of twin cabins for use as single cabins at a supplement to the normal one person fare, on certain itineraries. There are also cabin share programmes that will pair you with a traveller of the same sex to share a twin cabin.