There are usually quite a few people in your age group and that are single onboard ships. CCL and RCI are two of the more popular with singles. You will also see more singles on the shorter 3/4/5 day cruises. In addition those cruises that are during school breaks agains usually have more singles. You can pretty much stay away from Bermuda cruises, cruises over 8 days, cruises on lines such a HAL, Celebrity, Costa, Cunard, Crystal, Seaborn.