In the early hours of Oct. 13, the crew from the HS Dignity gathered on the deck of the cargo ship and put on life jackets as the vessel rocked in the churning waves of the Black Sea. The captain had given the order to abandon the vessel because it was sinking after a sea drone struck its hull.

As the 16-man crew, made up of Syrian and Egyptian nationals, peered into the darkness, they spotted the outline of a boat moving quickly toward them. They shone their flashlights, thinking rescuers might have already responded to their distress call. But what they saw alarmed them. No one was driving the boat.

“We realized that this boat was also part of the group that was attacking us. Of course, we all ran,” said Ashraf Mamdouh, the vessel's 42-year-old chief officer. The sea drone rammed directly into the ship.

“The vessel began sinking rapidly into the water. The whole crew was falling to the deck; nobody could stand properly because of the impact and the chaos,” he said.

“We didn't have time to finish launching the lifeboats.”The Dignity is one of nearly 50 commercial vessels that maritime analysts say have been attacked in the Black Sea this month as the conflict between Russia and Ukraine escalates at sea.

The strikes have brought much of the traffic through the key shipping corridor to a halt and prompted NATO to step up maritime security, including by deploying more patrol boats and radar. More than 30 killed or missing At least 31 seafarers have been killed or are missing in the attacks.

Many of the vessels that were recently attacked were travelling through the western Black Sea, including some that were struck off the coasts of NATO members Bulgaria and Romania.

On Friday, a search-and-rescue operation was underway after a ship flagged to Comoros, a small archipelago off the coast of East Africa, was struck by drones just outside Romania's territorial waters.

The crew of 13 included Ukrainian and Azerbaijani sailors. One body has been recovered, while officials say three people remain missing. Romanian President Nicușor Dan blamed Russia for the attacks.

Data shared with CBC News by maritime risk management firm Ambrey suggest there have been more than 500 attacks on commercial vessels this year in the Black Sea and the Sea of Azov, which are connected by the narrow Kerch Strait.

Of the 45 attacks recorded in October, Ambrey believes Russia was responsible for 40.

Russia's Ministry of Defence has acknowledged striking dozens of ships this month alone in social media posts, almost always claiming the vessels were supporting Ukraine's military.

But Mamdouh, who spoke to CBC News from a hotel in Varna, Bulgaria, said the Dignity had sailed from Algeria and was headed for Romania, where it was scheduled to pick up grain.

Adrift in the Black Sea The Dignity had already been at sea for more than a month when the drones struck at about 1:30 a.m.

Mamdouh and other experienced crew members urged everyone aboard to get as far away from the ship as possible to avoid being pulled under as the 123-metre vessel sank beneath the churning waves.

“We tried to gather together to reduce everyone's fear and panic. We wanted to remain in one group so that, if a rescue team arrived, it would be easier for them to rescue as many people as possible,” Mamdouh said. He began calling out to other crew members, but the strong winds drowned out their voices.

“I started asking everyone, ‘Why are you moving away from each other?’ I hadn't realized that I was drifting away, too. The sea currents were separating us.”At one point, a life raft suddenly appeared beside him. He climbed aboard and lay there for four hours, until another commercial vessel appeared nearby.

Still clutching his cellphone, he switched on its flashlight to attract the attention of the crew aboard the Azov Concord.

18-year-old among the missing Mamdouh was pulled from the water and is one of five crew members who survived. Eleven remain officially listed as missing, including 18-year-old Hamza Suleiman, a Syrian who was on his first voyage aboard a ship.

“The last phone call between Hamza and me was on the night of Oct. 12,” said his father, Basel, who spoke to CBC News via Zoom from Tartus, Syria.

“Hamza contacted us and said hi to his mother and reassured us. He said, ‘Dad, we're in Bulgaria now.’”Basel said his son had taken the job aboard the Syrian-owned ship because he expected to work in the engine room, where he hoped to learn more about engineering.

But he became disillusioned when he was assigned to work on the deck. He grew increasingly fearful after learning that another vessel, the Alfa Watan, had been struck by drones on Oct. 6. Ten crew members aboard that ship, most of them Syrian, have yet to be recovered.

After the Alfa Watan attack, Suleiman spoke with his son, who said he wanted to leave the vessel.

Basel Suleiman told CBC News he tried contacting the ship's owners to arrange for his son to disembark in Turkey, but the young man remained aboard.

Mamdouh, who spoke with Suleiman's father, told him that the last time he saw his son, the young man was aboard the ship wearing a life jacket. That detail has helped sustain his father's hope that he might still be alive. Basel agreed to speak publicly about his son despite the uncertainty surrounding his fate.

“We don't have the ability to reach the [Bulgarian] authorities or to go and look for our children with our own hands,” he said.

Khaldoun Nabelsi, head of the Syrian Seafarers Association of the U.K., said he had been in contact with several families whose relatives had been killed in strikes on commercial vessels. He said he had counted at least 18 Syrian seafarers killed.

“Nobody is forced to take these jobs, but in other ways you are forced. If you want to work, you have to go,” Nabelsi said.

“They have to find a deal to stop this. But from our side, as a seaman or as a shipping company, we can do nothing.”The deteriorating security situation has prompted the Philippine government to issue a directive prohibiting its citizens from boarding vessels navigating the northern stretches of the Black Sea.

Shipping companies scale back operations Some shipping companies that normally operate in the region are avoiding it altogether or have sharply reduced the number of vessels they deploy there.

Turkey-based ED Shipping has a fleet of 26 vessels, but 19 are currently “laid up,” meaning they are temporarily out of service and not operating at sea, said the company's chief financial officer, Demre İşcen.

One of the company's ships, the Circon, was struck on June 5 while transiting the Sea of Azov. Two crew members were killed.

Ukraine carried out the attack, acknowledging that it had targeted five vessels that night, including ships stationed at occupied Ukrainian ports. Ukraine said the vessels were involved in transporting stolen Ukrainian grain, as well as military cargo and fuel.

İşcen disputes that account, saying the Circon was on its way to a port in the Sea of Azov near Rostov-on-Don, Russia, where he said the company had a contract to load Russian grain.

“Our crew members are Azeri and Turkish nationals. We didn't have anything to do with Ukraine. We didn't have anything to do with occupied-area grain … stolen grain, whatever,” he told CBC News in an interview from Istanbul.

“Ninety per cent of the time, we carry grain cargo from Russia to Turkey, Bulgaria, Romania, Moldova, Georgia, Greece, all around the Mediterranean, Aegean Sea, Red Sea, Black Sea. This is our main trading area.”İşcen said the company was losing millions of dollars every month and that some of its seafarers were out of work because its ships were no longer travelling to Black Sea ports. Other mariners say they will refuse any work in the region.

Mamdouh remains in Bulgaria with the other surviving members of the Dignity's crew. They are waiting for new documents so they can leave Europe and fly home. “I will not go back to the Black Sea again. Never,” he said. “This situation is too dangerous.”