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Sub-Ice Search and Rescue with Mini-ROVs

Kiara Vallier   |   April 15, 2016

Search and rescue (SAR) teams are constantly facing ever-changing dangers during open-water recovery missions. Battling currents or undertow through unclear conditions can quickly lead to exhaustion for divers. Dive teams are also subject to depth limits, oxygen levels, and pressurization stops, making extended searches arduous. Recovery through ice and frigid temperatures introduces a completely new set of challenges.

What is Ice Rescue?

Ice rescues occur when a person, vehicle, or asset has fallen below the ice shelf of a body of water. Regardless of the status of the rescuee, the response team will need to immediately devise a plan to limit the exposure to freezing temperatures. How this plan is enacted depends on whether they are faced with a surface or subsurface rescue.

Surface Rescue

Surface rescues refer to when a victim or asset has fallen through the ice sheet, but has maintained a topside position. Ideally, if the surrounding ice is strong enough, victims can quickly gain enough grip for a self rescue. If the ice sheet is too weak, or if the rescuee has lost too much energy for a self rescue, a surface rescue commences.

Coast Guard Rescue

Credit: Coast Guard Rescue

As mentioned above, self rescue teams will always begin by attempting to coach the victim through a self rescue. If successful, no member of the SAR team will be put at risk. If this is unachievable, the team may be required to venture onto more stable portions of the ice to extend a retrieval hook or pole. At this point, rescuers should be prepared to potentially enter the water and be equipped in a PFD and full dry suit. If the victim has lost too much strength to maintain a hold on the retrieval device, full entry will be required. The diver will enter the breach area and attach themselves to the victim for extraction.

Subsurface Rescue/Recovery

A subsurface rescue occurs if a victim or asset has plunged underneath the surface ice sheet and is unable to reorient themselves above water. Since the victim has now entered a drowning state, and rescuers have lost sight, the situation becomes more complex. Divers will quickly equip a harness to tether themselves to land before entering the water. Once deployed, divers will scan the area and retrieve the drowning victim. Diver Rescue

Due to the extreme conditions, subsurface rescue missions have a critical hour for retrieval. This is commonly referred to as the ‘golden hour’. If response teams are unable to rescue the victim from the ice before the first hour ends, focus shifts from rescue to recovery. At this point, urgency declines to increase diver safety while conducting a dignified body recovery.

Steps to Performing a Sub-Ice Rescue

1. Ice Dive Training and Certification

Due to the dangers associated with diving in sub-zero temperatures, a specialized Ice Diver certification is required. This is to be completed on top of an SDI Open Water SCUBA Diver certification. Ice diver courses provide education about the effects of cold on the body, different equipment used in ice diving, and surfacing procedures. At the end of training, students will be required to demonstrate their skills on land as well as perform a live dive.

Police forces and fire departments in cold climates regularly conduct ice diver training. This ensures that they are well prepared to handle emergency situations year round. In 2015, Deep Trekker was fortunate enough to be invited to attend the annual sub-ice dive training hosted by the Ottawa Police. Every year police forces from around the province gather to discuss and practice under-ice search and rescue techniques.

2. Prepare and Assemble the Team

Establishing the roles and responsibilities of each SAR team member is crucial for a smooth rescue operation. Understanding each divers’ capabilities and assigning roles accordingly allows for optimized entries and extractions. For example, those who perform the best at gearing up may be selected as divers, while others who excel at cutting entry points can act as land members to cut entries, hold tethers, and provide comms.

Team Assembling

In a perfect scenario, each team member would immediately snap into their respective role and conduct the mission. In practice, things may not go as planned. For this reason, it is integral to familiarize each team member with contingency plans. This includes identifying backup divers, ensuring there is adequate backup equipment, and cross training the whole team on diving, cutting, and tethering techniques.

Once a call is received and the team is deployed, each member should feel confident about their core role, and also have the capabilities to react to adaptive situations. The SAR team will proceed to have divers gear up in a dry suit, full face mask, and carry a backup regulator. Once on the scene, the designated entry cutters will get to work.

3. Locating the Victim

If the rescuee is still able to stay afloat, the SAR team can immediately commence surface rescue methods. If the victim has already sunk below the surface and is no longer visible, the team will quickly devise a search strategy to locate the missing person.

Search and Rescue Tent

The Circle Search Method

A common search pattern for subsurface searches is the circle method. Relatively simple, the circle search method has a diver swim in a series of circles around a fixed reference point, gradually increasing the circumference.

The circle search is best for searches where the area of the target is known with relative accuracy. If the initial breach point is easily identifiable, this is typically the reference point. The radius of the circles depends strongly on visibility and underwater conditions. There should be a small overlap between the current circle and the previous circle to avoid the risk of missing the target. If the target is not found by the time the circle search has been completed, the team may shift the center point and then start again.

Grid Search Method

To simultaneously search multiple areas of interest, SAR teams can create a grid across the search area. Using markers, teams create search squares covering the area to be searched. Much like previous methods, the size of the search squares depends on visibility and the size of the target. After the search squares are created, each section is thoroughly searched. Following the completion of each square, searchers report and log anything of interest.

One common variation on the grid search method is the compass grid search. In this pattern the diver swims parallel lines on a compass bearing and its reciprocal while conducting a visual search. The lines chosen often allow for overlap to ensure accuracy.

Read our full article on SAR Tactics here.

4. Rescue

Once the drowning victim has been located, the SAR team can begin rescue procedures. With a sub-ice rescue, victim retrieval is complicated since it is impossible to make a direct resurface. Instead, the primary diver will need to be directed by their tender. The ‘tender’ is the team member responsible for holding the tether and communicating directions to the diver. Their surface position and tether control allows them to understand the diver position and guide them back to the entry point. Once the victim is retrieved, emergency medical procedures can begin.

Use ROVs to examine hazardous areas in your search and rescue missions

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Steps to Performing a Sub-Ice Recovery

Once past the initial hour of rescue, chances of survival dramatically diminish and the mission objective shifts from rescue to recovery. The same steps for rescue should be followed while conducting a recovery, however priority should be given to safety rather than speed. Each team member will fall into their assigned roles and begin performing search tactics to locate the victim. Different equipment may also be utilized, since priority equipment is best served in emergency rescue missions rather than recoveries.

Depending on the circumstances, recovery missions can last for days or weeks. Strong currents or murky conditions can result in rapidly changing environments with near-zero visibility. Precarious environments like this make searches difficult, and generally lead to extended timelines. At the 2-3 week point, decomposition can make recoveries more sensitive, and SAR teams may consider specialized tactics for a dignified retrieval.

The Dangers of Submerged Ice Search and Rescue/Recovery

Unpredictable Ice

Ice conditions can vary dramatically depending on the type of water body, location on a water body, or weather conditions. Ice conditions can change quickly, so walking on ice is never guaranteed, even if the conditions have been assessed as safe. Team members need to take precautions when cutting an entryway to ensure they don’t fall in and become a victim themselves.

Sub Ice Rescue Dangers

Not only are ice sheets dangerous for navigating to the optimal entry point, but they also cause unpredictable surfacing techniques. While some ocean or lake conditions may have intermittent open areas for resurfacing, these pockets are never guaranteed. Ice divers should always be tethered and managed to a tender for safe guidance back to the original entry point.

Limited Oxygen

During cold weather rescues, divers will burn more oxygen in comparison to their warm weather counterparts. This is because the human body is constantly using oxygen to keep its internal temperature stable. In conjunction with limited resurfacing, this additional oxygen consumption means divers should pay careful attention to their gas levels.

Ice divers will utilize the rule of thirds for oxygen management. While conducting the search, divers will need to monitor their tank levels and aim to use one third of their oxygen swimming away from the entry, one third swimming back, and save one third for malfunction issues.

Equipment Malfunctions

Equipment is inspected before a dive, however in extreme temperatures, any malfunction can be fatal.. Sub-ice recovery divers should always be adequately trained on methods to avoid common equipment issues. Passive tactics to avoid regulator freeze-ups as well as mask fogging should be constantly implemented once in the water. Primary divers should deploy with two first-stage regulators and a backup second-stage in the event of a malfunction, as well as have a backup diver on standby for assistance.

The Advantages of Using an ROV for Ice Diving in Search and Recovery

Improve Visibility Underwater

Remote Operated Vehicles (ROVs) are submersible robots that utilize HD cameras to inspect submerged objects. For SAR, they can quickly be deployed and instantly start a victim search in a matter of minutes. In the event of unclear or dark conditions, ROVs can be equipped with auxiliary lighting and imaging sonars. These sonar feeds provide unmatched visibility through murky water in comparison to the human eye.

Sub Ice Rescue ROV A Deep Trekker ROV identifying an object with 15m (49ft) using the M3000 Oculus Sonar.

Additionally, an ROV can also be equipped with positioning systems. This enables the SAR team to track the vehicle’s position on a map and plot waypoints for areas of interest. If the victim is identified by the ROV, the rescue team will immediately have precise map coordinates for deployment.

Decrease the Risks to Divers

One of the main challenges of search and recovery is the environment, often unpredictable or unknown; with cold temperatures, ice cover, wind and strong currents posing risk to the safety of the diver.

Having an ROV on standby for SAR missions can benefit diver safety in two ways. Firstly, having an ROV in the water can act as a monitoring system for the divers. If any breakdown of communication occurs, the vehicle can provide a visual update on the diver’s status. In the event of a tether break, the ROV can also substitute in as a reliable line back to the entry hole.

Secondly, since the vehicle can act as a primary diver during search missions, it lowers the number of people required to enter the water. No matter how effectively an ice diver has been trained or the quality of their equipment, every dive carries a risk. The only way to completely eliminate the chance of injuries or deaths is to keep humans out of the water.

Improve Search Times

ROVs can deploy extremely quickly since they require no thermal equipment, oxygen, or other safety precautions. This is crucial in the initial stages of a SAR mission and can be the difference between a rescue vs. recovery.

Additionally, ROVs can generally operate for between 4-8 hours on a single charge in comparison to 30 minutes for a diver. This extension of search times allows for more effective searches. In the event of a recovery mission, the time capabilities between ROVs and human divers compounds and can exponentially decrease the overall search time.

Interested in learning more? Check out our comprehensive article covering ROVs for search and recovery here.


ROVs’ running on batteries rather than topside power benefit from a compact form factor. This enables them to be easily transported or carried. Being able to quickly navigate to different drop points or transport the ROV in any vehicle is extremely beneficial for quick SAR response times. Many rescues take place in remote locations, so being able to arrive with an ROV via ATV or snowmobile provides unparalleled flexibility.

Sub Ice Rescue ROV in Water

Increase Searching Distances

Ice divers are usually restricted to tether lengths of 100m as a safety precaution. In the event of a malfunction, the tether should be short enough for a rapid withdrawal. Since there are no concerns of safety over an ROV, tether lengths can extend up to 700m (2295ft). This enables the SAR team to cover immense distances without cutting new access points, which saves valuable time.

How Deep Trekker Improves Sub-Ice Search and Recovery

Deep Trekker designs all their ROVs to be capable of operating in waters between -5C to 40C (23F to 104F). This allows for year round usage in nearly any climate. Additionally, depending on the model, Deep Trekker ROVs can drop to depths between 200m (656ft) and 305m (1,000ft) for deep water missions. With no concerns about pressurization, this can save critical time during rescues.

Deep Trekker offers three different ROV models to fit every budget, each with their own unique specialties. The DTG3 is the lowest cost and is extremely nimble and compact. The entire system transports in one Pelican case and deploys in under a minute for crisp HD visuals with impressive battery life. The REVOLUTION and PIVOT ROVs offer enhanced power for control in turbulent conditions, more robust addons, and increased depths.

Intelligent addon capabilities are the key to an optimized ROV experience. Deep Trekker offers a variety of imaging sonars, physical manipulators, and positioning systems that are excellent for SAR. Integration of sonar with the REVOLUTION or PIVOT ROV provide operators with vision though murky conditions between 0.1m (4 inches) and 200m (656ft).

USBL positioning sensors allow for team members to map the ROV location and mark multiple waypoints as areas of interest during a mission. Additionally, modular grabber arms can be mounted on any Deep Trekker ROV. These claws allow the ROV to latch onto a variety of objects, either for direct retrieval or to offer a direct tether line to a target.

ROV display showing Sonar Feed and USBL Positioning A Deep Trekker ROV display showing Sonar Feed and USBL Positioning.

Impressive systems alone aren’t enough to provide a best-in-class experience. Deep Trekker’s intuitive robots are extremely sophisticated, yet simple to deploy and pilot. All packages include a weatherproof controller housing a 7” screen, tether, and reel. Since the ROVs are incredibly easy to operate, they require minimal training which allows for seamless operation across team members.

For more information about each ROV Package, check out our in-depth ROV Buying Guide.

As always our team of experts is available to answer any questions you may have. Reach out about a customized quote or product demonstration today.

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