Another approach to the digital aquarium (as seen at the London Aquarium):
http://cswww.essex.ac.uk/staff/hhu/v...wim2005Aug.avi
12.7MB
Fully autonomous, designed and made by a team led by Professor Huosheng Hu of the University of Essex. "They move forward and if they find an obstacle, they turn. They have several behaviours depending on the situation." They have infra-red and pressure sensors. The tail has three joints.