Apparently, barnacles are a big problem for ships, which is why the Navy deployed their own version of an underwater Roomba to take care of the hulls of their ships. The Hull Bug is a robotic vacuum especially made for taking care of this problem.
The Hull Bug is made by Sea Robotics and is currently being tested by the Navy for another 2 years. The Hull Bug is a lot more complicated than a Roomba because it needs its own sensors and algorithms, as well as functioning as a fully automated submersible. Of course, it also has to be fully waterproof and cling to the hull of a ship too. The little robot is less than 3 feet long and weighs less than 50 pounds.
Barnacles can decrease the speed of a ship by 10% and increase fuel consumption by 40%, so something like this is critical to maintaining ships.