According to the interlocutor of Interfax, the dock and the submarine sank due the poor technical condition of the dock.

This is the second such incident in a week. On December 12, Rosmorrechflot (Russia’s Federal Agency for Maritime and River Transportation) reported that a submarine which was sent for disposal partially sank in the Sea of Japan while being towed. 

The SPD-16 floating dock was laid in 1938. It is a pontoon metal structure for repair of submarines, destroyers, minesweepers, and supply vessels with a displacement of up to 5 thousand tons. During World War II, repairs were carried out on it on warships and submarines. After the war, he was stationed in Sevastopol, where ships and auxiliary vessels were repaired on it.

Maritime Business World