The Palau-registered 2,113 dwt livestock carrier was reported to have capsized in the port of Midia, near Constanța, on Sunday morning.
All 22 crew on board the vessel were rescued, with one seafarer taken to hospital with hypothermia. The Queen Hind is owned by Astra Marine Services and managed by MGM Marine Shipping, both Romanian companies, according to Equasis.
An operation has been launched by the Romanian Coastguard, police and firefighters to rescue some 14,000 sheep on the vessel. Some 32 sheep were rescued having been found swimming in the sea, while many were believed to have drowned.
A video of the capsized vessel above shows sheep hanging from the side of the stricken livestock carrier and swimming in the sea.
The cause of the accident is not known.