The two 125,000-ton vessels being built by Mitsubishi Heavy Industries for Carnival's German AIDA brand will incorporate MHI's Air Lubrication System to achieve a 7% fuel savings. The MALS system will force air bubbles under the ship's hull to create a cushion of air flowing under the ship which will allow it to move through the water with less friction resulting in lower fuel usage and less CO2 emission.
The system has been in use for several years on cargo vessels built by MHI, but the AIDA vessels, set for delivery in 2015 and 2016, will be the first cruise ships to employ the MALS system.
The animation below from Mitsubishi shows how the system works.