Near the base of the monolith is a peculiar hole of unknown origin. Some believe that the rock was used as defence during the Caucasian War and the hole was created to shoot through at the enemy. However, this is doubtful because although Sail Rock is thin, it is still not easy to puncture. This observation is supported by an incident described by the Russian writer, essayist and journalist S.Vasyukov, where he saw a Russian battleship shoot 4 projectiles at the monolith. “Although the traces of the cannonballs were visible, but the cliff was nowhere to be destroyed,” he wrote.
Why a battleship shot at such a spectacular natural wonder is something one will wonder. Thankfully, Sail Rock was declared a natural monument in 1971 and is now protected, at least, from man’s harm, for the sea continues to erode the stack away. Aerial photographs of Sail Rock show submerged rock extending as much as 90 meters away from the monolith indicating the "sail" was much longer at earlier times.


Source