*1.2.3 Autonomous underwater vehicles (AUVs)*

The most recent developments in remote sensing are the growth of autonomous underwater vehicles which are also known as unmanned underwater vehicles (UUV) or remotely operated vehicles (ROV) [10]. AUV's are commonly used in oceanographic monitoring and are becoming more popular for industrial applications and environmental monitoring. These new machines have demonstrated to be cost-effective, efficient, and safe alternatives [11] for water quality assessment and monitoring. They employ the same "deploy and forget" ethos as autonomous sensors. It is possible to mount multiple water quality sensors on board the vehicle which can then be deployed in remote areas. AUV's require tether connections for them to be powered and controlled, this is done via fibre microwave transmissions, fibre optics, remote controllers, communication media and satellites so that they can receive and send data [11]. The hulls of these devices are becoming smaller as the need to minimize manufacturing resources increases, cutting down on power, fabrication costs and time [12] are all important aspects for the new wave of AUV's.
