Seventy percent of the earth is surrounded by water and there may be lots of raw material still unexplored. A human being cannot dive longer because breathing could be one of the major constraints. For the deep-sea applications like debris removal, pipeline inspection, surveys, telecommunications support, research, maintenance, there must be need of some technology which can venture down without any constraints. Underwater robots technology is the best solution to this because robots do not have to breathe like a human being. But there are problems in case of underwater robots. One of the major problems is trajectory control of the link. Because of dynamic coupling between the base and the link, on which various forces acting on the link and manipulator, the arm deviates from its desired trajectory in the presence of buoyancy forces. This dissertation work presents the dynamic modeling and trajectory control of underwater robot using bond graph, which include the base of the plant, one link arm and the motor. The underwater robot is modeled with the integration of the overwhelming controller. The integrated bond graph model is also made for the complete underwater vehicle. Modelin