Poseidon is the largest torpedo ever developed in any country. At around 2 meters (6.5 ft) in diameter and over 20 meters (65 ft) long, it is approximately twice the size of submarine launched ballistic missiles (SLBMs) and thirty times the size of a regular ‘heavyweight’ torpedo.

On 20th February 2019 Russian president Vladimir Putin announced that the first submarine slated to carry Poseidon would be launched in Spring 2019. This is most likely to refer to the Pr.09852 Belgorod which had been expected to be launched in 2018. The same day the Russian Ministry of Defense released a video (Youtube) of the Poseidon being tested.