The Magazine for Underwater Professionals

Jul/Aug 2016


Miko introduces magnetic sledge for underwater object retrieval

The sledge being deployed off Norway

Norway-based Miko Marine has introduced a magnetic sledge that is capable of retrieving ferrous objects “as small as a fingernail” from underwater. Measuring two by one metres, the sledge is made from aluminium and equipped with 10 powerful permanent magnets. When towed over the seabed the sledge can pick up objects that may be covered by sand or silt and achieve results that would be difficult or impossible for divers to equal, according to the company.

A spokesman said: “Each magnet is suspended independently beneath the sledge from a flexible mount that enables it to pass over rough or broken ground without damage or becoming snagged. Capable of working at any depth, the sledge can be equipped with a video camera and an acoustic positioning system such as a Sonardyne (UK) Scout linked to a GPS chart plotter. This enables it to follow an accurate search pattern and ensure that nowhere is missed.”


The sledge is typically fitted with buoyancy to offset the weight of the magnets so it can be handled efficiently and for the height at which it is towed above the seabed to be precisely controlled, the spokesman added.

The Miko magnetic sledge is a potentially useful tool for police and accident investigations. One was recently used to successfully recover parts from a Super Puma helicopter that crashed into the sea near Bergen, Norway. The aircraft went down with the loss of two crew and 11 passengers during a flight from the Statoil Gulfaks-B platform. It went into relatively shallow water close to the shore near Turoey and subsequently caused the world’s fleet of Super Puma helicopters to be grounded until the cause of the accident is known.

Although much of the wreckage was quickly recovered, accident investigators were anxious to study the helicopter’s transmission. The Accident Investigation Board of Norway consequently commissioned Miko Marine to design and build a sledge that could be used to recover ferro-magnetic debris hidden beneath the seabed around the crash site.

  • The sledge in use underwater

Miko Marine is a salvage technology company that has particular expertise in the use of magnets. Responding to the urgency of the request, Miko engineers were able to design, build and deliver the sledge within four days.

“The sledge was operated from a 12-metre workboat catamaran that surveyed an area of seabed measuring some 400 by 700 metres, working 12-hour shifts over a period of two weeks,” said the spokesman. “By the end of the search a number of metal objects had been recovered for analysis including the vital components from the helicopter’s transmission system.”

New mini-ROV launched

USA-based Aquabotix reports the introduction of a new mini-ROV, the Endura.

Engineered for dependability and functionality across a wide range of underwater applications, the surpasses other mini-ROVs in thrust, dependability and software performance, according to the company.


“Endura is easy to use – it is ready for the water in three minutes, basic driver competency is developed in about three hours, with professional proficiency achieved in three days. Endura is intelligent – a full computer is built inside the vehicle and auto controls are available in the software. Endura is high performance – with hydrodynamic design for ultimate control in the water and powered by high-torque motors for up to five knots of thrust,” Aquabotix said.

The Endura configuration includes: five precision high-torque motors; a sensor package including depth, temperature, digital compass and leak detector; a 1080p true HD quality camera with tilt; 60 metres of neutrally buoyant tether; a depth rating of 100 metres (a 300-metre depth rating is also available); six pounds (2.7 kilograms) of payload capacity for customer specific applications; and high intensity LED lighting (4400 lumens).


The ROV operates on lithium battery technology with a standard operational run time of four hours. Available as an option, AC power can be used for continuous operation. Other options include: sidescan, scanning or multibeam sonar; GPS, DVL, USBL, Wi-Fi, Bluetooth, satellite communications; environmental sensors; fish plow, laser scaler, manipulator arm; and 360-degree rotating/180-degree tilt camera.

KRISO cuts the tether
  • KRISO's 'Crabster'

Underwater communications equipment that enables video to be transmitted through the water and unmanned vehicles to be controlled without a tethered link to the surface has been supplied to the Korean Research Institute of Ships and Ocean Engineering (KRISO) by Sonardyne Asia Pte Ltd in Singapore.  

The BlueComm 100-series optical modems will be used to stream high-definition imagery from cameras installed on seafloor sensor platforms and command Crabster, an auto-nomous walking and flying crab-like robot being developed by KRISO’s ocean systems engineering department. 

Transferring data using subsea modems provides a reliable alternative to using cables underwater which can be expensive to install and vulnerable to damage. However, unlike conventional acoustic-based devices that use pressure waves to send and receive relatively small packets of data at low bandwidths, Sonardyne’s BlueComm uses rapidly modulated light emitting diodes (LEDs) and high-power lasers to quickly deliver very high volumes of data.  

Typically operating in the 450 nanometer Blue Light region of the spectrum, data rates of up to 500 megabits per second are achievable making the technology suitable for a wide range of underwater applications that require a high bandwidth, low latency, bi-directional communications link. These include harvesting data from seabed landers using AUVs, remote video monitoring of science operations and piloting unmanned vehicles without the need for a control umbilical. 


When deploying battery-powered subsea instruments and vehicles, operating life is always a major consideration for users. BlueComm’s unique method of optical data transmission is, however, also highly efficient, enabling for example one gigabyte of data to be transmitted with the energy contained within a single lithium ‘D’ sized cell over distances greater than 150 metres. 

The BlueComm modem family is currently made up of three variants and to support its work, KRISO has selected the BlueComm 100 model. Featuring Ethernet connectivity and a deep depth rating, the design is optimised to offer a good balance between data rate and range in all conditions, including high ambient light. 

Anthony Gleeson, vice president of Sonardyne in Singapore, said: “Now that it’s possible to send and receive data underwater at speeds comparable to domestic broadband, it’s exciting to consider the huge range of potential applications for BlueComm.”

He added: “KRISO is the first institute in our region to invest in BlueComm and we are delighted that this unique technology will help to advance its pioneering ocean research.”





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