This paper deals with guidance and control of a newly developed autonomous underwater vehicle named Aqua Explorer 1000 for inspection of underwater telecommunication cables up to 1000 m in depth. The guidance and control process for altitude keeping control from seabed and depth keeping control in the longitudinal plane is discussed here performing the numerical simualations and the experiments at a towing tank and at sea. The control strategy for altitude control and depth control was proposed and tested successfully by using fuzzy algorithm. Optimization of fuzzy controller was successfully performed based on the mathematical dynamic model of the vehicle. Adaptive fuzzy controller for altitude control consisting of fuzzy controller, system identfication block and output modification block was proposed to keep the effectiveness of fuzzy controller in unknown circumstances such as irregularly wavy seabed.