Russian secret subs

This shows how spy subs were deployed from a larger one.

Piranha (Project 865, NATO - Losos)
With two boats entering service in the the early 90s, the Piranha class were purpose built special operations craft. The post-Soviet Russian Navy did not see the need to operate dedicated craft and they were discarded in the early 2000's after attempts to sell them abroad were unsuccessful despite considerable interest in the design.
An interesting feature is the two tubular storage bins for SDVs / diver propulsion devises which give the craft a characteristic hump back.

http://covertshores.blogspot.com/2010/08/russian-soviet-sf-underwater-craft.html