The deaths of two Navy SEALs who drowned during a mission to intercept Iranian missile parts bound for Yemen’s Houthi rebels were preventable, an investigation has found. Chief Special Warfare Operator Christopher J. Chambers and Navy Special Warfare Operator 1st Class Nathan Gage Ingram drowned in January while boarding an Iranian smuggling vessel.

An outside investigation concluded that the deaths were due to insufficient safeguards during the mission. Rear Adm. Michael DeVore, who led the investigation, stated that the SEALs lacked essential failsafe systems and buoyancy measures that could have saved their lives. He noted that there were “deficiencies, gaps, and inconsistencies” in the mission’s planning and execution, which left the SEALs vulnerable to the rough conditions they faced.

The SEALs disappeared on January 11 during a nighttime operation targeting an Iranian ship suspected of smuggling weapons to the Houthi rebels. Chambers fell into the sea while boarding the vessel, and Ingram attempted to save him. Both sailors, weighed down by heavy equipment, drowned within seconds.