Shore based excursions are very important for the cruise lines as they make large profits for the companies.
For example, it is estimated that Navigator of the Seas, owned by Royal Caribbean, makes up to and even over a million dollars a week in on board sales and sales of shore excursions. It is usually the safest option for the passengers to book via the cruise lines as they normally try hard to make sure that the businesses they are working with are safe for their passengers, as well as licensed.
Previously if there was an accident to a passenger on a shore excursion, even one sold via the cruise line, the cruise line could often rely on the defense that the excursion company was an independent contractor and therefore they could not be held to be liable. However, more recently, the courts have started to apply some of the principals of common law hence the cruise lines have a higher duty of care.
For example, if they use words in the literature about the excursion such as highly skilled employees run the excursion or they say the excursion is safe, and there is an accident then the cruise line can be held liable.
In the case of Zapata versus Royal Caribbean, the passenger bought an excursion via the cruise line for bell diving. The passenger ran out of air under the water and was brought to the surface for oxygen, only to find the oxygen tank was empty and so he died. In another case, a passenger bought an excursion to a beach from the cruise line, Carnival Corporation but on the way back from the excursion there was gangland violence on the road and the passenger was killed. It was ruled that Carnival knew about the gang violence in the area and knew that the beach had a reputation for drug and gangland related violence and the company was therefore negligent in offering the excursion to passengers.