ANKARA, Turkey, July 31 (AP)--A British diver is preparing an expedition to determine whether a shipwreck discovered off the coast of Istanbul is the remains of a vessel carrying Jewish refugees fleeing the Holocaust that was torpedoed and sunk, killing more than 750 people.

Turkish divers say that earlier this month they located the wreck of the Struma, believed to have been sunk by a Russian torpedo in February 1942. The ship is in water 80 meters (264 feet) deep off the coast of Istanbul.

British diver Greg Buxton is leading an expedition to Turkey to verify whether the wreck is the Struma. Buxton's grandparents were among the 779 passengers--mainly Jews from Romania--who had boarded the ill-fated streamer hoping to make their way to Palestine. Buxton and his 13 other team members arrive in Turkey next week.

"For me the expedition has an added meaning," Buxton said Monday, speaking by telephone from his home in Birmingham, England. "After all, it is my grandparents' grave."

The rickety, 45-meter-long (150-feet-long) Struma sailed from the Romanian port of Constanza in December 1941 but quickly broke down. Turkish tug boats helped it reach an Istanbul harbor.

The passengers were forced to spend 2 1/2 months aboard the ship in cramped, squalid conditions while Turkish officials tried to convince British authorities to let the passengers travel to Palestine. Britain was restricting immigration to Palestine at the time.

Turkey, which was neutral during World War II, refused to allow the refugees to disembark. Turkish tug boats towed the ship back to the Black Sea on February 23, 1942. It was attacked a day later.

Only 21-year-old David Stoliar survived the attack.

Levent Yuksel, a diver with Turkey's Underwater Research Society, which found the wreck earlier this month, said all evidence points to its being the Struma.

"Its length, its depth, its stern are identical to the Struma," Yuksel said.

Stoliar, who now lives in Oregon, in the United States, and some 40 relatives of the victims will hold a Jewish memorial service for the dead in Istanbul in September even if the shipwreck is not identified as the Struma.

"We need to hold the service now because some of the relatives are in their 90s," Buxton said.

There are no plans to raise the vessel, but Buxton hopes that artifacts found in the ship could eventually be put on display at Holocaust museums in the United States and Israel, as well as in an underwater-artifacts museum in Turkey.