ROV

A remotely operated vehicle is an underwater robot connected to the surface by a tether. That tether, usually called an umbilical, carries electrical power down and video and telemetry back up, and a pilot flies the vehicle from a control station on a vessel, on a platform, or increasingly from an onshore operations room. The tether is both the defining constraint and the defining advantage: it limits range and adds drag, but it removes any need to carry energy on board and keeps a person in the decision loop for work that requires judgment.

The industry sorts vehicles by capability rather than size. Observation-class systems carry cameras, lights, and enough thrust to hold position in mild current. They are electric, often small enough for two people to deploy from a workboat, and they have absorbed much of the inspection work that once required divers: hull and propeller checks, harbour structure surveys, net inspection on fish farms. Work-class vehicles are a different proposition. They carry manipulator arms, tooling skids, and sonar, they need hundreds of horsepower delivered down the umbilical, and they require a launch and recovery system plus deck space on a suitably equipped vessel. Between the two sits a light work class with a single manipulator and modest tooling.

Power delivery shapes the engineering. Sending kilowatts down a long umbilical means transmitting at high voltage and stepping it down inside the vehicle. Traditional work-class designs converted that power into hydraulic pressure to drive thrusters and tools; electric drive is now common where efficiency, control resolution, and the absence of hydraulic fluid matter. A tether management system, either a top hat that rides on the vehicle or a cage it flies out of, decouples the vehicle from vessel heave and pays out a short neutral tether at depth.

Specifying a system starts with depth rating, thrust and payload, manipulator reach and degrees of freedom, sensor interfaces, and the vessel and crew the spread will need. Resident systems, which stay docked subsea and run on demand over existing infrastructure, change that calculation by taking the vessel out of routine work.