Have you ever wondered how gargantuan cruise ships move through the waters from one port to the next? With power sources quickly changing within the industry thanks to environmental demands, it's the type of fuel used to power cruise ships that clearly divides the old from the new. Those drawn to the high seas will find a range of options when it comes to how their cruise ship is powered.

Traditional Methods of Power

Diesel. This is the most simple and traditional power source available. Similar to steam ships, which faded from the scene in the late 20th century, engines are fueled by the ignition of diesel, which has become the new standard. Like steam, this drives the engine's pistons up and down. This energy turns the crankshaft up to thousands of revolutions per minute. Attached to the crankshaft is the propeller, which then turns at a more efficient and leisurely pace of roughly 250 revolutions per minute. While the boat is out at sea and moving quickly enough, energy harvested from the propeller shaft through a generator can be used for for electricity onboard, making good use of the energy output.

Diesel electric. Very similar to "direct diesel" above, diesel electric is designed to make the ship's energy use the most efficient it can be no matter the speed. In this case, the engine is connected to generators that produce electricity. From the generator, this electricity turns the propellers. Generators often have back ups in separate rooms in case of fire to prevent a total electricity outage as well as generators to convert the high voltage to a lower voltage for cabin use for things like hairdryers, which require around 110 volts.

Gas Turbine. Though it is a non-renewable resource, ships powered by gas turbine are a greener option. Similar to the diesel electric, gas is used to spark and power generators that then produce electricity to turn the propellers. Additionally, the heat from the turbine's exhaust steam is often used to power electricity onboard.

Environmentally-Conscious Operations

Many cruises have taken numerous precautions to cut down on single-use plastic, electricity needs and even redesigned ships with more aerodynamic shapes to become more environmentally-friendly. Though the ships still require diesel or gas, there are options to supplement energy use onboard.

Celebrity Cruises' Solstice ship has 216 solar panels which power services such as the elevators and lights and reduce the need for fueled energy by 50 percent. Before used engine oil is left at port cities, the boat also separates it from the water to ensure the waste is not being discharged in the ocean.

In addition to its non-toxic coating which creates less resistance as the boat propels through the water, Disney Cruises turn more than 1,000 tons of ocean water into drinkable water everyday. Water from the air conditioning units, nearly 300 tons per day, is used to do the ship's laundry.

Finally, Star Clippers boats are 70 percent wind-powered. The cruise line is also home to a team of biologists who conduct research at ports in both the Mediterranean and Caribbean.

How to Choose a Voyage

As cruising, which is the fastest growing tourism sector, continues to grow and green travel continues to emerge as a trend, travelers can more easily find options that appeal to their interests and values. Once travelers understand what it is they desire from a cruise, be it shopping, food, spas, time on the beach or local, authentic experiences, the best cruise line can be chosen.

While routes determine how much time is spent on land or at sea, every cruise company has a niche, though they often appeal to all as well. Families love Disney Cruises because the ships and entertainment are tailored to kids while providing parents with plenty of appealing activities too. Princess Cruises are known for the exceptional and wide range of dining options. Celebrity and Royal Caribbean cruises are best for young adults traveling in couples, groups or alone. For an experience away from the run-of-the-mill, Star Clippers and Intrepid Travel both offer sailing expeditions, the greenest option available. While Intrepid's trips are for smaller groups, Star Clippers includes a fleet of tall cruise ships.

Once the best company for the type of trip or destination is decided, simply search for the company's energy use to find current statements and efforts toward environmental impact as well as the latest technologies the cruises are using to offset their carbon footprint. With industry-wide steps forward, any cruise line will offer more green options. Additionally, what is good for the environment has become good for the cruiser. Today, many cabins have tinted windows to decrease the need for air conditioning; therefore, rooms are cooler even with large windows or balconies. Be sure to book above the lowest deck to ensure a sound night of sleep away from the buzz of the engine.

Disclosure Leaf Group is a USA TODAY content partner providing general travel information. Its content is produced independently of USA TODAY.