Robotics @ Maryland's ( http://ram.umd.edu ) Autonomous Underwater Vehicle (AUV) Tortuga follows two sections of an orange pipeline. This is in the Space Systems Lab's ( http://ssl.umd.edu ) Neutral Buoyancy Research facility.
This is the height of over a year of work by 20 students at the University of Maryland ( http://www.umd.edu ). At last years 2007 AUVSI International AUV Competition ( http://auvsi.org/competitions/water.cfm ) about 1/5 of the years teams were able to follow any sections of the orange pipe. Only three were able to follow multiple sections as Tortuga has done in the video above.
This work was made possible by the hard work of vision team, and our recent addition an additional two thrusters which allows for sideways motion.