Halibut (Project 18511 (Paltus))

The Project 18511 Paltus (NATO reporting name: Halibut) is a class of Russian deep-diving special purpose nuclear submarines. These highly classified vessels are designed for intelligence gathering, underwater research, and supporting deep-submergence vehicles.

Developed by the Malakhit Design Bureau during the late Cold War, the Project 18511 class was conceived as an advancement of the earlier Nelma-class to conduct covert deep-sea espionage, salvage, and cable-tapping operations. The lead vessel of this upgraded design, designated AS-35, was laid down in the late 1980s and officially entered service with the Russian Navy in 1995. Operated by the highly secretive Main Directorate of Deep-Sea Research (GUGI), these midget submarines are transported to mission sites by specially modified nuclear-powered mother ships to perform sensitive missions in the Arctic and North Atlantic. Today, the Paltus remains active within the Northern Fleet at the Olenya Guba base, maintaining a critical role in Russia's undersea warfare infrastructure.