Last week, an Indian Kilo class submarine, the INS Sindhughosh, that was coming to the surface near the port of Mumbai (Bombay), collided with a merchant ship. It was a glancing blow, and received minor damage to the conning tower. The merchant vessel suffered some minor hull damage. A year ago, the U.S. nuclear sub USS Newport News suffered a similar accident in the Straits of Hormuz (the entrance to the Persian Gulf). The Kilo class boats displace 2,300 tons, while the Newport News is about three times larger.

In both cases, problems with sonar (used for navigation when near the surface) were believed to be the cause. This is a growing problem whenever subs operate near populated areas (that tend to have lots of ship traffic.) There have been a growing number of incidents like this in the last decade.