A boat trying to sneak in 250 immigrants from the Middle East to Australia capsized in rough seas off East Java, Indonesia on Saturday. Some 185 passengers went missing while 15 drowned.

A Pakistani survivor, one of 34 rescued by passing fishermen after clinging to the wreckage for eight hours, said the six Indonesian crew of the fishing vessel, including the captain, abandoned them after big waves broke up the boat.

"The captain and six crews took the life vests and started swimming away. They were all from Indonesia. We lost sight of them in the big waves and we never saw them again. We don't know if they were rescued," said 18-year-old Saed Mohammad Zia, according to Adelaide Now.

The boat, which can only carry 100 passengers, was crammed with 250 Iranian, Pakistani, Afghan and Turkish asylum-seekers when it overturned at 6 a.m. local time on Saturday. The survivors were brought to Prigi beach.

Indonesian police said the refugees, including about 40 children, arrived in Jakarta earlier last week without legal immigration documents. They were taken by bus to a port en route to Christmas Island.

Authorities believe each asylum seeker paid people smugglers $5,000 for the voyage to Christmas Island, which is located in the Indian Ocean 2,600 kilometres northwest of Perth.