If you are going on a cruise alone, chances are you'll be asked to pay a higher price, usually called a "single supplement". This can represent up to 50% of the trip cost, since it is designed to make up for the income a second traveller would have generated. However, many cruise lines now realize that most seniors are solo travellers, and they have designed what they call Senior Singles cruises. Senior Singles cruises offer low-cost single supplements or guaranteed share options.
A guaranteed share in Senior Singles cruises is when you book a cruise with a roommate chosen at random by the line as to discharge your single supplement. If the Senior Singles cruises line is unable to find you a roommate the price will be reduced.