A South Korean ferry sank slowly Wednesday night, leaving almost 300 people unaccounted for. The South Korean government said more than 160 had been rescued. (Reuters)

A South Korean ferry capsized Wednesday with 459 aboard, most of them teenagers on a high school trip. Here is what we know so far:

Where did the boat capsize?

The boat ran into trouble several dozen miles from Jindo, an island that sticks out of South Korea’s southwestern corner like a little toe. Jindo is surrounded by a group of even smaller islands that are slightly farther afield from the mainland. The ferry was curving around those small islands at the time it issued a distress call.

What caused the disaster?

We don’t yet know, and it’s important not to turn the few pieces of information into something conclusive. But some passengers report feeling a jolt or hearing a loud noise just before the ferry began to capsize. This would be consistent with the ferry running aground or colliding with a rock or some other enormous object.

How cold is the water?

Various reports place the water at 50 to 54 degrees Fahrenheit. One emergency official told the Associated Press that a survivor could develop hypothermia after 90 minutes in such waters. Many of the survivors were rushed to Jindo Island and were given thick blankets and dry clothing.

How deep is the water?

It’s about 110 feet deep, relatively shallow. The ferry itself is 480 feet long. Hours into the rescue, the ferry’s bow could be seen protruding from the water, the rest of the vessel submerged. It’s conceivable that one end of the ferry was touching the floor of the Yellow Sea as the other end poked out of the water.

What do we know about the ferry’s journey?

The ferry was making a 13-hour, 30-minute trip from Incheon to Jeju. Incheon is a port city to the west of Seoul and a major departure point for vessels heading not only to South Korean islands, but also to China. Jeju is a volcanic island and the southernmost major point in South Korea. It’s famous for its lava-rock beaches, seafood and eclectic museums; it has museums dedicated to sea shells, teddy bears, sex and Africa.

The island has a population of just 600,000, but it attracts some 10 million visitors annually, including armies of Chinese tourists, who are allowed to visit without a visa.

What is it like to ride a South Korean ferry?

South Korea has several thousand islands, and ferries connect the largest ones. The vessels come in all sizes, but the long-haul ones — suited for overnight trips — tend to be well-appointed. The Sewol had multiple decks and bedrooms for passengers, as well as a restaurant, a library, a convenience store, according to a video on the Web site of the ferry operator. South Korea's Yonhap news agency says that the Sewol was built in 1994 in Japan.