Want to a go on a green vacation? Don’t head out into the blue. According to USA Today, an environmental group says the overall grades that cruise lines earn for their green efforts “aren’t pretty.”

San Francisco-based Friends of the Earth has unveiled its second annual report card on the environmental impacts of 11 major cruise lines and 113 ships. The group graded the cruise lines on sewage treatment, air pollution reduction, water quality compliance and accessibility of environmental information.

Crystal Cruises, which appeared on the list for the first time this year, scored the lowest grade of F. Carnival and Silversea each scored a D-, the same as last year. Royal Caribbean showed improvement, raising its grade to a D+.

Disney Cruise Line received a C-, but was praised for its recent installation of advanced water treatment systems on its ships. Holland America, Norwegian Cruise Lines and Princess did the best, earning grades of B-. As for individual ships, the group gave top grades of A to Holland America Oosterdam, Westerdam and Zuiderdam and Princess’ Coral Princess and Sun Princess. To view the entire report card, click here.

The ratings caused immediate controversy. The Cruise Lines International Association put out a statement calling Friends of the Earth “a campaign fundraising group” and saying the criteria in the survey was “arbitrary and flawed.”

Marcie Keever, director of the Clean Vessels Campaign at Friends of the Earth, said the group believes cruise lines can do more to be green, such as end the use of dirty fuel and stop dumping sewage and other waste into the sea. ”We understand that cruise ships and cruise vacations aren’t going anywhere and it can be a reasonably priced vacation especially for families, and you can choose all sorts of things to do on your cruise,” Keener said. “But for people concerned about the environment this (report) gives people an opportunity to make a choice about what ship or line they can take.” She also warned, “You can’t assume all ships are fine.”

Does being green factor into your vacation? Is price more important than the environment?