Because the cruise ship industry is one which runs on seasonal highs and advantageous weather for cruising, seeking employment by the season makes some logistical sense. High seasons for the cruise industry are the summer months, spring break weeks and during the winter holiday season. In addition to requiring more employees to satisfy the demands of this busy time, cruise lines are almost always hiring and don’t adhere strictly to the beginning or end of specific season. This means, for college students or workers who are employed by other seasonal occupations, working in the cruise industry during a specific season can be a good choice. 
Typically however, cruise lines like to employ staff who have some interest in long term employment and applicants who express this interest are often at an advantage. Students should avoid thinking they can pick up cruise ship jobs on a season by season basis and if they are restricted to work of this kind, should look into cruises that are seasonal specific or other land tour seasonal jobs rather than applying as a normal employee.
There are some seasonal-only jobs that exist in the industry, like Alaskan cruises or summer riverboat jobs. Alaskan cruises only run in the summer for obvious weather-related reasons and are a good place for seasonal employees. Looking to smaller ships and jobs on yachts is a good choice for the seasonal employee. This is again because the industry is driven by a higher interest during peak months and the work staff thus, must be larger to comply.
Some summer cruise ship jobs are land jobs. This includes staff members who stay on land in a specific location (Alaska, for instance) and meet passengers as they arrive from different cruise ships. Jobs such as these can be adventure tour guides, photographers, sales representatives or informational speakers for the port. While jobs like this are excellent for the seasonal employee, they can be difficult to procure and should be well researched and applied for well in advance. Other seasonal jobs are entertainment positions, which require performers to play seasonal ‘characters.’ For example, cruise lines hire actors to play Santa during the holiday months and to partake in holiday related performances.
Because work on a yacht seems to be driven by seasonal changes, researching high seasons for yacht and riverboat travel and then applying for work in those specific regions will help meet your seasonal employment goals, especially if your seasonal time off is non-traditional.
Some of the best seasonal work opportunities are for tour guides. These employees are usually not hired by cruise ships (although they can be). As a result, the perks and salaries are different from those of cruise ship employees, but usually offer benefits of their own. For the adventure seeker and outdoor lover, touring mountain bike groups or river rafting expeditions is a dream come true for filling seasonal gaps in employment and are perfect because they are driven by favorable weather.