For a trip that revolves around fresh air and miles of endless pristine ocean, cruises do an awful lot of environmental damage. For example, the Queen Mary 2 uses so much fuel that its miles-per-gallon average is about 41 feet, requiring about 4,381 metric tons of fuel per voyage. The Sapphire Princess generates the same amount of sulfur dioxide as 13.1 million cars every day. Additionally, according to the Environmental Protection Agency, a cruise ship carrying 6,000 passengers generates about 210,000 gallons (800,000 liters) of raw sewage per week — most of which is dumped directly in the ocean, as long as they are at least three miles from shore. And that doesn’t even include the oil-rich bilge water dumped on a regular basis as well.