The Deepest Point: 2.80 meters
Specialists from the Underwater Activities Group studied the marsh step by step to determine depth and bottom composition. They replicated the crossing that led to the two deaths to clarify the circumstances surrounding the incident.
A captain who led the exercise in 2019 explained that a platoon of sappers had surveyed the lake beforehand. That platoon was removed from service by Defense in 2020.
“The lake’s deepest point is 2.8 meters,” the report notes. “From the route’s start to the first 15 meters, water depth is 1.80 meters, but at 25 meters it reaches two meters and then rises further thereafter.” This implies that, using 1.80 meters as a difficult-to-foot depth, the December 21, 2023 drill would have required moving roughly 90 meters while afloat.
Additionally, “the ground varied between firm, hard zones and soft mud or dirt,” and the bottom consists of silt or mud, except at the very start and end where it is rocky.
Security Platoon Deactivated
The marsh’s characteristics and the exercise’s level of difficulty are crucial to the investigation. Documentation sent by the commanding officer to the Regiment’s Jefe de Plana Mayor, and approved by the Regiment’s Colonel, reportedly contained no details about the planned route, depth, or other aspects, nor any request for material support or assistance from other units, according to the summary.
Moreover, the unit responsible for assessing the lake’s state was “deactivated in 2020 by decision of the Army General Staff.” The diving and navigation squad of the engineers battalion did ensure safety in earlier years, according to two captains who supervised the river crossing then.
In 2019, Terrain Was Analyzed beforehand
“I carried out a first exercise in 2019 designed to cross the marsh without foot contact, supported by engineers who had previously surveyed it. During the passage, undertaken in pairs, they had water support and a diver for each pair,” one officer told the Guardia Civil. A second captain who performed the exercise in June 2021, after being denied sapper support, said he altered the route and directed the troops to cross areas where water never covered the ground.
Investigators concluded that the concurrence of conditions during the drill led to the deaths of the two soldiers. Missing amphibious support, the lake depth, and the nature of the bottom were cited, along with the low temperatures endured by the deceased and their peers, as contributing factors.
Loss of Body Heat
Meteorological data indicate the scene began in chilly conditions: air temperatures near freezing, high humidity, and early-morning cold. At the time the soldiers reached the lake, temperatures hovered around 4.3°C with 82 percent humidity. When the exercise commenced, temperatures around 6.8°C with 70 percent humidity were recorded.
Documents state that the drills began at five in the morning, with temperatures around 3.9°C. Personnel described waiting until nine o’clock for the crossing, after completing earlier marches and clearing obstacles.
The Guardia Civil concludes that the unusually cold temperatures and the waiting period contributed to body heat loss. Entering the water, where heat loss is significantly faster than in air, likely worsened the situation.
Backpacks and Medical Support
Another key factor is the packs carried by the soldiers. Investigations indicate some packs were not properly sealed, diminishing buoyancy. This was identified as a fundamental factor for the proper execution of the exercise.
Regarding medical support, plans existed, but the responders were in another area of the base—specifically in the firing ranges where exercises were also underway that morning.
No Immediate Medical Attention
“Once alerted, medical services arrived at the marsh promptly, yet could not treat the soldier who was unconscious with water in the lungs.” A sub-lieutenant who happened to be present and heard cries provided initial care. Another soldier was simultaneously drowning, and a third soldier who exited the water in a semi-conscious state did not receive immediate medical attention. Nonetheless, the Guardia Civil concluded that the presence of an ambulance and on-site medical staff would not have changed the fatal outcome for the two deceased soldiers.
Overall, the investigation highlights how the interplay of difficult terrain, inadequate equipment, cold conditions, and moments of delay converged to produce the tragedy at Cerro Muriano. The findings emphasize the need for complete planning, on-site readiness, and robust safety measures when crossing water obstacles during military drills.