It is about 30km wide at its narrowest point, which at the north end, but this is a short section, about 30km long, and then it opens out to about 100km for another 100km. There are a number of small islands in the strait; the volcano Krakatoa is located on one of them.
As one of the two main passages from the South China Sea to the Indian Ocean (the other one being the Straits of Malacca), the Sunda Strait has long been of significance to navigation. Despite the dangers due to its narrowness and rocks, it is much shorter than the Malacca strait, and consequently ships would run fewer risks from pirates.
In early 1942 the Battle of Sunda Strait was fought here, a Japanese force sinking the USS Houston and HMS Perth as they attempted to prevent the landings on Java.