French military divers assisting in the recovery operation at the wreck of the MV Barima say extreme underwater conditions—including complete darkness, strong tidal currents and a tangled interior filled with ropes and hammocks—are making it exceptionally difficult to locate and recover those still missing from Guyana’s worst maritime disaster.

The grim assessment was shared with relatives during a briefing at the Charity Operations Centre on Sunday, where members of the French Armed Forces outlined the challenges they have encountered since joining the multinational recovery mission earlier this week.

“We arrived on Monday, and since Tuesday we have committed about 15 dives on the wreck,” one French military officer told family members.