This ship hull grooming robot was designed to remove marine fouling deposits (which translates to about $500 million in maintenace and fuel costs) from the hulls of ships, eliminating excess drag.

The Robotic Hull Bio-inspired Underwater Grooming (HULL BUG) is similar to an autonomous vacuum cleaber that uses a biofilm detector to differentiate between clean and unclean surfaces. The HULL BUG detects the presence of microorganisms and cleans the hull before a colony of barnacles (which eats up fuel and reduces the speed of a ship) is built.

Source: Eco Friend