For some specialized missions, an ROV powered from the shore has its uses. However, for most types of ROV operations, a battery-powered ROV like the Aquabotix Endura or Hydroview Sport has the clear advantage. There are three main factors that make running an ROV from battery power the better choice.
First, battery power is portable. A battery-powered ROV can be deployed anywhere the ROV can be carried to, and the lightweight ROVs made by Aquabotix can be carried by one person to almost any location on Earth. Battery-powered ROVs can be deployed from the beach, from a small boat, from an oceangoing ship, from an offshore platform – if a person or vehicle can get there, then a battery-powered ROV can go with them and engage in missions from that spot.
Second, battery power is compact. The person or team deploying a battery-powered ROV does not need to carry a bulky generator with them to remote areas in order to send the ROV on missions. They can carry the charged ROV to the entry point and work from there without needing any expensive and heavy infrastructure. This makes a one-off mission even in the remotest areas simply a matter of putting the charged ROV in a vehicle (or even a backpack) and heading out.
Third, because radio waves do not carry well underwater, all non-autonomous ROVs use a tether to provide control and communication with the operator. In an ROV that relies on shore-based power, this tether also carries the electrical power the ROV uses for its operations. That means the tether must be much thicker for a shore-powered ROV. For example, a typical power-carrying cable might be [X – Beats me <g>] millimeters in diameter, while the tether for an Aquabotix ROV has a diameter of only [X] millimeters. Of course, a thicker tether is also a heavier tether – 250 meters of standard power-carrying tether weighs [X] kilograms, while the same Aquabotix tether weighs only [X]. This makes moving and deploying the battery-powered ROV much simpler and easier.
Battery-powered ROVs are simply easier to deploy, easier to carry, and able to operate in places that powered ROVs cannot.