The cruise ship arrives once a while to stay for about 25 minutes. It gives to an opportunity to do the sex starved ladies on board. The major advantage to doing one's regular cougars is the larger penis growth. While normal cougars will give you a 0.03-0.04mm gain, action on the cruise ship earns you up to 0.1mm. Especially useful at low levels because the benefit shrinks as the game proceeds.
Apart from that, there is still money to be made. Especially the top position frequently offers an impressive salary, five figures are possible. The downside of jobbing on the ship is that the conditions to be met are higher than normal. E.g., to satisfy the number one on board, you will always(?) need the maximum excitement.
One final note for last minute jobs: If you accept a job during the last minutes (2, 3 or so), you are unable to finish it before the ship leaves. As a result, you, the passenger without a ticket will be discovered and thrown overboard. You end up in hospital with the usual consequences (loss of health, candy coin costs/timeout).