Hundreds of Indonesian rescuers have widened their search for dozens of missing people after a ferry sank in rough seas on the way to the resort island of Bali on Friday, with six bodies recovered.

The ferry carrying at least 65 people, including passengers and crew, was making a five-kilometre (3.2-mile) crossing from eastern Java Island to Bali when it tilted and sank in bad weather late Wednesday, witnesses and officials said.

As of Friday morning, 30 people were still missing after 29 were plucked from the water to safety.

Rescuers said one of the six found dead was a three-year-old boy.

Tearful survivors described their horror when the ship went down, including one man who lost his wife.

"I was joking around with my wife. And then the ferry tilted. The accident was very fast," Febriani, who like many Indonesians has one name, told AFP late Thursday.

"I resigned my fate and asked God to save my wife. It turned out my wife died but I survived," said the 27-year-old, welling up with tears.

"I jumped with my wife. I managed to get back up but my wife slipped away."

Rescuers carried out searches by sea and air on Friday, expanding their efforts along the coastlines of eastern Java and Bali, national search and rescue agency operations official Ribut Eko Suyatno told reporters.

"The land search rescue unit we ask to comb through the Ketapang beach from north to south. likewise, for Gilimanuk," he said.

But as of Friday afternoon, no further victims had been found.

"From the communication that we received, it's still zero (victims found) from the search," Yudi, a captain of one of the deployed rescue vessels, told broadcaster Metro TV.

The ferry passage from Java's Ketapang port to Gilimanuk port on Bali, one of the busiest crossings in the country takes around one hour and is often used by people travelling between the islands with a car.

Local rescue officials said the KMP Tunu Pratama Jaya vessel sank 25 minutes into its journey.

At least 306 rescuers were deployed Friday for the search effort, the Java-based Surabaya search and rescue agency said.

The search was temporarily halted overnight and resumed around 8:00 am (0000 GMT) Friday in Bali.

Rescuers had deployed inflatable boats, larger rescue vessels and a helicopter to aid the search on Thursday, made up of dozens of personnel, including navy and police officers.

At least four survivors were found early on Thursday after saving themselves by climbing into the ferry's lifeboat.

Initial search efforts were hampered by bad weather, with waves as high as 2.5 metres (8 feet) and strong winds.

The ferry's manifest showed 53 passengers and 12 crew members but it is common in Indonesia for the actual number of passengers on a boat to differ from that document.

Marine accidents are a regular occurrence in Indonesia, a Southeast Asian archipelago nation of around 17,000 islands, in part due to lax safety standards and sometimes due to bad weather.

In March, a boat carrying 16 people capsized in rough waters off Bali, killing an Australian woman and injuring at least one other person.

In 2018, more than 150 people drowned when a ferry sank in one of the world's deepest lakes on Sumatra Island.