What is the splash zone? (2024)

The splash zone is frequently defined as a non-accessible area and poses significant challenges to operations in offshore wind, oil and gas, fish farming, and transport infrastructure. But what exactly is the splash zone? And what are the challenges in splash zone operations?

In areas with harsh environments, such as in the North Sea, it is common to assume that offshore structures located in the splash zone are not easily accessible for cleaning, inspection, repair, or modification. In fact, the world’s largest classification society, DNV, describes the splash zone as a non-accessible area.

But what exactly is the splash zone?

DNVs Offshore Standard DNV-OS-C101 provides greater detail:

«The splash zone is the part of a support structure that is intermittently exposed to seawater due to the action of tides or waves. The splash zone separates the atmospheric zone and the submerged zone, and is determined by the influence of waves, tidal variations, settlements, subsidence, and vertical motions.»

At OceanTech, we define the splash zone as the part of the structure immediately above (+20 feet) and below (-50 feet) the waterline. The condition and integrity of offshore structures in the splash zone are affected by corrosion, fatigue, and marine growth.

Corrosion, fatigue, and marine growth

The splash zone is not only a major challenge in the offshore oil and gas industry; underwater structures in offshore fish farming, offshore wind, and transport infrastructure, are also located in harsh marine environments. Steel structures, mooring systems, pipes, risers, fish farming nets, and monopiles are all exposed to aerated seawater, UV radiation, and repeated wetting and drying.

If left unchecked, the conditions in the splash zone can result in various serious problems, including:

  • Accelerated corrosion on exposed surfaces
  • Accelerated material strength fatigue
  • Marine growth, such as algae and mussels, in some cases up to three feet thick

The potential for a neglected problem to turn into an expensive issue is considerable. In offshore oil and gas, for example, plant failure and unplanned maintenance account for nearly half of overall efficiency losses. The notoriously unpredictable splash zone, however, poses real challenges for those involved in the cleaning, inspection, repair or modification of offshore assets.

Challenges in splash zone operations

Waves and structure-induced currents are ever-changing but always present in the splash zone, making it difficult for divers and remotely operated underwater vehicles (ROVs) to perform inspections and maintenance work. Although a significant proportion of structures are aging and in urgent need of inspection, splash zone operations are often perceived as too complex, too costly, or too hazardous.


Unlike deep-water environments, where divers and ROVs can function relatively undisturbed, the dynamic splash zone presents a number of specific hazards to both humans and technology. Variations in weather conditions, in particular, combined with the proliferation of pipework in the splash zone, create unpredictable circ*mstances for divers and ROVs.


Traditional splash zone operations using divers and ROVs may be both time-consuming and costly. The normal diver window is only a few days, and work is highly dependent on favourable weather conditions. This means that the estimated costs of a work scope can increase significantly. There are also direct costs involved. Splash zone maintenance and repair has traditionally required the use of a diver support vessel at an approximate cost of EUR 180,000 per day.


The difficulties presented in this environment can often make it too dangerous to work using traditional methods, such as rope access and diving. While working in confined spaces, crush injuries are always a risk, and the swell can disturb buoyancy and make it difficult to hold an exact position while working.


Offshore energy companies need to adhere to regulations, as well as design and operational standards. Environmental regulations, in particular, are becoming increasingly important. Non-compliance with laws and regulations can lead to heavy fines and possibly further complications. Owners of splash zone areas thus have a huge responsibility to ensure that equipment is maintained in accordance with the regulations.

OceanTech’s splash zone tools

What we are seeing is that the offshore wind, oil and gas, and fish farming industries are increasingly focused on finding alternative solutions to traditional methods. At OceanTech, we offer a wide range of innovative tools and techniques, from lightweight robotic solutions to more heavy-duty solutions with industrial standard robotic arms. All the tools and techniques are designed to avoid any use of divers, ROVs, or support vessels.

The technology is developed for all underwater cleaning, inspection, repair, and modification services, and can be launched from any offshore structure. Our capabilities include:

  • Remotely operated robotic solutions for the cleaning of marine growth, or the removal of corrosion prior to inspection or repair
  • Visual and NDT services for the splash zone and underwater structures. Our robotic solutions provide a stable platform that enables the deployment of inspection tools which would be impossible using divers and ROVs
  • All repair solutions required in the splash zone, including corrosion protection, reinforcement, wrapping repair, and surface blasting
  • Modification services in the splash zone, including modifications of existing structures such as offshore platforms, bridge columns, port constructions, offshore wind turbines, and fish farming structures

Our services are often offered as a turn-key solution, and provide several benefits, including cost savings, efficiency and safety gains, reduced CO2 emissions, and regulatory compliance:

  • With no need for divers, ROVs, or support vessels, our innovative approach delivers superior cost savings in comparison to traditional methods
  • The technology is highly efficient and operates using all standard types of ROV subsea tooling. It offers great HSE benefits too, as there is no manual handling involved
  • Our robotic solutions are environmentally friendly, as they reduce CO2 emissions significantly by reducing the need for support vessels
  • We are familiar with both offshore regulations and requirements, in addition to design and operation standards. Our track record includes multiple operations in the North Sea, the Gulf of Mexico, and Australia

By utilizing OceanTech’s technology, the splash zone is no longer a non-accessible area.

What is the splash zone? (2024)
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