Safety and risk profile
Divers bring remarkable skill, but their exposure to entanglement, impact injury, and the risk of decompression illness makes safety management complex; long shifts, cold stress, and low visibility compound this. ROVs remove people from the water—a major improvement—but the deck remains a dynamic work site, and tethers introduce entanglement and handling risks. Access robots keep personnel out of this environment, shifting the highest-severity hazards from ‘people exposure’ to ‘equipment exposure’. Operators work from a topside control container, with built-in safety features, dual-point securement and defined retrieval procedures.
In short, robots provide the most consistent risk reduction; ROVs offer significant—but task-dependent—mitigation; and divers carry the greatest inherent risk despite robust professional controls. At OceanTech, we have achieved over 250,000 incident-free offshore work hours, demonstrating the reliability of our technology.
Weather windows and uptime
The splash zone punishes operations with short, unpredictable weather windows. Access robots are engineered to hold position across tide cycles and moderate to rough sea states (up to ~3 m Hs), using tracks, clamps or magnetic adhesion to ride out surge while maintaining tool contact. This design widens workable windows and reduces costly stop-start cycles.
Divers face strict limits: visibility, current, surface chop and vessel motion can halt a dive before it starts, and even brief deteriorations trigger pauses or aborts. ROVs fare better than divers but still struggle when wave aeration and surge degrade thruster authority and sensor performance.
Practically, robots extend productive hours per day and per campaign, trimming standby time and uncertainty. That steadier cadence is especially valuable on multi-asset programs where small daily gains compound into meaningful schedule reliability.
Environmental footprint
Minimising the dispersion of biofouling and protecting protective coatings are key environmental objectives. Access robots provide stable tool engagement and, depending on configuration, can incorporate debris capture or low-water/low-pressure cleaning systems that reduce plume formation. Because the machine holds steady against the structure, operators can adjust removal settings precisely rather than relying on brute force against the environment.
Divers generally avoid chemical cleaning, but variable technique in surge conditions can increase dispersion and make local containment difficult. ROV jetting or cavitation can strip biofilm effectively, yet in the aerated splash zone the resulting plume disperses quickly, while higher thruster power raises energy demand.
A further distinction is vessel use. Unlike diver or ROV operations, access robots are deployed directly from the platform and do not require a dedicated support vessel. This not only reduces cost but also removes the largest single source of emissions in splash-zone cleaning.
Across all methods, the cleanest results come from stable, well-controlled removal within clearly defined operating envelopes. Robots make that level of control achievable at scale and allow environmental performance to be documented alongside quality-assurance data.
Cleaning quality
Effective cleaning in the splash zone is about controlled contact: applying enough force to remove marine growth without damaging coatings or substrates. Access robots excel in this role because they maintain stable, repeatable pressure and travel speed, with tool heads — whether brushes, cavitation devices or water-jet nozzles — kept on specification by the machine rather than influenced by the sea state. The result is uniform surface roughness and predictable coating preparation.
Divers can achieve excellent local results thanks to human dexterity, but in turbulence quality may vary from section to section as visibility, fatigue and surge change. ROVs perform well against biofilm and light to moderate fouling using jetting or cavitation; however, heavy calcareous growth and coating preparation usually demand more sustained contact than a free-swimming vehicle can provide in aerated water.
For consistent quality assurance across large areas, access robots deliver the most uniform outcome.
Access and reach
Splash-zone structures are rarely flat: braces, nodes, appurtenances and coating systems all complicate access. OceanTech’s access robots are designed to conform to curved members, transition smoothly across welds, and navigate around clamps, anodes and penetrations. Positive attachment — via rails and clamps — allows tools to remain engaged across the air–water interface, where surge is most severe.
Divers bring unmatched dexterity in tight corners, but safety limits often restrict how long they can work these challenging areas. ROVs can manoeuvre into complex geometries, yet maintaining steady tool pressure while managing tether drag and surge is difficult.
In summary: for broad coverage of complex geometry at the interface, robots offer the best balance of reach and control; divers excel in one-off, intricate touch-ups; and ROVs suit light-touch access where required contact forces are low.
Cost of operation
Total cost is more than the day rate. Weather-related downtime, standby, vessel class and capability, crew size, and rework risk drive budgets. Access robots often deliver a lower total cost because they turn marginal weather into productive hours, reduce rework through consistent quality, and can be deployed from the platform or with smaller teams on smaller vessels.
Divers can carry higher hidden costs: narrow weather windows increase standby, conservative safety margins extend durations, and vessel requirements raise daily spend. ROVs are cost-effective for inspection and light cleaning, but heavy splash zone removal often lengthens timelines, eroding the initial advantage.
When you model a campaign with realistic weather loss and QA contingencies, access robots typically produce the most stable cost profile—less volatility, fewer surprises, and better predictability.
POB and logistics
Access robots typically mobilise with a compact footprint — the robot, a topside control unit, a power/hydraulic power unit (HPU), and a small toolkit — freeing deck space and simplifying lifts. OceanTech’s equipment and tooling are lightweight and deployed from the platform with specialised rigging techniques. This allows small crews of 3–6 platform-based personnel to perform tasks that diving teams or expensive ROVs struggle with or cannot complete.
Dive spreads, by contrast, are substantial: launch-and-recovery systems, gas management, a decompression chamber, communications, and a larger team. Set-up and demobilisation take time, and vessel choice is constrained.
ROV spreads sit between the two: the pilot console, winch and tether-management systems are manageable, but still require clear deck space and craneage.
Data capture, QA & documentation
Cleaning operations in the splash zone demand evidence: where you cleaned, how thoroughly, and in what condition the surface was left. Access robots typically integrate sensors, video and positional tracking to produce coverage maps, before-/after-imagery and parameter logs (e.g., pressure, traverse speed, number of passes). This package streamlines handover and simplifies audits.
Divers can record helmet-cam footage and notes, but positional accuracy and completeness vary with conditions and time pressure. ROVs excel at video documentation and can be georeferenced when conditions allow; however, in the aerated splash zone it is difficult to maintain stable framing and reliable positioning.
For QA-heavy scopes — coating preparation, NDT readiness or regulatory reporting — access robots provide the most comprehensive and repeatable data trail with minimal extra effort.
Productivity and speed
Robotic systems are built for long, steady shifts. Once secured to the structure, they maintain tool engagement and path control for hours. That predictability eases planning and minimises lost motion between starts and stops.
Divers are highly productive in short bursts, but mandatory decompression and rest, tool handling, and safety pauses reduce net throughput across a shift. In rougher water, even skilled teams see their pace vary widely. ROVs excel at rapid visual surveys and targeted interventions; however, cleaning productivity drops when surge forces frequent repositioning or when stubborn calcareous growth requires high, continuous contact force.
Over a multi-day scope, access robots tend to post the best average removal rates — less because of raw speed and more because they remain on task as conditions fluctuate.
Lastly, certain splash-zone cleaning tasks simply cannot be performed safely or compliantly by divers, nor viably by ROVs—yet they are routine for access robots. Think riser cleaning at the North Sea air–water interface, where breaking waves and surge demand continuous, high-contact force to remove calcareous growth and prepare coatings: divers face unacceptable impact risk, while ROV thrusters lose authority in aerated water.
The same applies to conductor and caisson splash zones around guide frames, where entrapment hazards and confined geometry rule out human-in-water work and snag ROV tethers.
Boat landings, ladders and fenders are another no-go: impact, limited clearances and turbulence prevent controlled tool pressure. Robots also enable debris-captured cleaning at J-tube mouths, cable protections and intake/outfall areas, where containment is critical and surge defeats diver-held skirts and ROV stability.
Finally, QA-critical uniform roughness over large jacket bays—for coating warranty or NDT readiness—requires logged pressure/speed and unwavering contact that only a clamped, tracked robot can deliver at scale.