Eighteen Ukrainian sailors were trapped underwater in their capsized tugboat after it collided with a cargo ship in Hong Kong waters Sunday according to a CNN article.

The Director of Marine Department said the sailors were trapped in the hull of the ship and that it was possible that they could still be alive if they found an air pocket inside their vessel. Rescue divers had knocked on the boat and did not hear the sailors signal back, unfortunately.

Divers made nine attempts to rescue the trapped sailors but were having trouble with strong currents and poor visibility.

The cause of the accident was not yet known and weather conditions were “reasonable” at the time the collision occurred. Neither vessel was overloaded.