Underwater Vehicles (ROVs): What They Are, How They Work, and What They Are Used For

An underwater vehicle is a robotic system built to work below the surface without a human on board. The most common type is the ROV (remotely operated vehicle): a tethered, pilot-controlled robot that carries cameras, sensors, thrusters and often manipulators, and is driven from a surface control station. Saab Seaeye, which describes itself as the world leader in electric underwater robotics, builds tethered, autonomous and hybrid electric robotic systems for missions in some of the toughest environments on the planet. Use this guide to understand how these vehicles work and what to weigh when choosing one.

What an underwater vehicle is — and the main types

Underwater vehicles split into a few practical categories:

• Tethered ROVs — connected to the surface by an umbilical that carries power and data. The pilot sees through the vehicle's cameras and controls thrusters and tools in real time. This is the workhorse type for inspection, intervention and tooling tasks.
• Autonomous systems (AUVs) — untethered, following a pre-programmed mission and returning with data. Useful where a tether is impractical or where survey coverage matters more than live control.
• Hybrid electric systems — combine electric drive with capabilities that bridge tethered and autonomous operation, giving flexibility across mission types.

Saab Seaeye's range covers all three, with electric propulsion as the common thread.

How an ROV works: components and operation

Main components

Typical operation

1. Deployment — the vehicle is launched from a vessel or platform using a deployment system (crane, winch or launch frame).
2. Piloting — the pilot flies from a surface control cabin, using camera feeds and sensor data to navigate and position the vehicle.
3. Work — the vehicle inspects, surveys or intervenes using manipulators and tooling, with power and data flowing through the tether.
4. Recovery — the vehicle is brought back aboard and data or samples are retrieved.

The key mechanism is the tether: it is what separates an ROV from an autonomous vehicle, because it allows continuous power and real-time control rather than a stored energy budget and pre-set mission.

What underwater vehicles are used for

Saab Seaeye lists sectors that map closely onto the general uses of ROVs:

• Oil & gas
• Renewables
• Telecoms
• Salvage
• Hydro & civil engineering
• Aquaculture
• Marine science & academia
• Seabed minerals
• Nuclear
• Leisure & tourism
• Civil security & emergency
• Military and defence

In practice, these uses share a common pattern: work in water too deep, too dangerous or too costly for divers, where a pilot needs to see and act in real time.

Choosing a vehicle: what to compare

When comparing ROVs, use the same dimensions across options:

• Depth rating — the maximum working depth the vehicle is built for.
• Payload — how much tooling, sensor or manipulator weight it can carry.
• Thruster configuration — how many thrusters and how they are arranged, which affects manoeuvrability and holding position in current.
• Electric vs hydraulic tooling — electric manipulators and tools suit electric vehicles; hydraulic manipulators and Hydro-Lek specialist tooling serve heavier intervention tasks.
• Deployment and control — whether you need a control cabin, a specific deployment system, or a more compact setup.
• Mission type — tethered for live intervention, autonomous for survey, hybrid where the mission changes.

For example, a marine science team doing repeat visual surveys has different priorities from a salvage operator that needs to grip and cut — the first leans on camera and sensor payload, the second on manipulator and tooling capability.

Where to go next

Saab Seaeye's site organises its offering into Sectors, Solutions (including Underwater Vehicles, Electric Manipulators, Deployment Systems, Control Cabins, Defence Vehicles and Hydro-Lek Tooling), Support (product support, after-sales support and training), and Contact (including a distributor network). If you are specifying a vehicle, start from the sector closest to your mission, then check the vehicle and tooling options against the comparison dimensions above.