During the operation -- in which the elite troops boarded a vessel off the coast of Somalia in January -- one SEAL slipped and fell into the water, while a second jumped in to try to help him.

"Encumbered by the weight of each individual's gear, neither their physical capability nor emergency supplemental flotation devices, if activated, were sufficient to keep them at the surface," according to the Navy investigation, which said the incident was "marked by systematic issues" and was "preventable."

It found that the SEALs were "not well-practiced in using their emergency gear," with some operators saying they had only used their flotation systems once, and others not at all.

Maintenance of the systems also did not meet Navy standards, with the investigation saying it is possible that the SEALs "attempted to activate their emergency devices, yet they somehow failed to activate."

And it noted that the SEALs had not conducted buoyancy tests in theater, where conditions were different than during training, and that there was conflicting guidance on buoyancy requirements.

The US military conducted a 10-day search for the two SEALs before declaring them deceased.

Yemen's Huthis have been targeting vessels in the Red Sea and Gulf of Aden since November 2023 in attacks they say are in solidarity with Palestinians in Gaza -- a significant international security challenge that threatens a major shipping lane.

The United States has carried out frequent air strikes on the Huthis in a bid to degrade their ability to target shipping, and has also sought to seize weapons before they reach the rebels, but their attacks have persisted.