The Dolphin Class advanced Swimmer Delivery Vehicle (SDV-X) was developed in the 2000s as a US export type based on the SDV Mk.VIII Mod-1 Gator Class SDV in service with the USN SEALs. 
All articles
Piranha SDV-X
The Piranha was a two-man SDV marketed by The Columbia Group in late 2000s: Read More
SDV History - US Closed-Cycle Energy Source SDV project
In the late 1980s, during the final days of the Cold War, the US Navy SEALs were looking towards a new generation of SEAL Delivery Vehicles (SDVs). One of the advanced designs in circulation was the Closed-Cycle Energy Source (CCES) submersible.
SDV History - Lesser known Anglo-French projects
Probably one of the sleekest SDV designs out there; a family of two, four and five-man diver transports developed by MAREX.
300mph home-build Supercavitating midget submarine
Ever fancied burning from Canada to France in 13 hours, under water?
Spy Subs - New photo of Losharik
There are few active submarines as elusive as the Russian 'Special Projects' boat 'Losharik' so this new photo is something of a find! 
First DDS - Type-IIIA U-Boat
Although never built, the German Type-IIIA submarine was to be the first designed with an integral dry deck shelter for smaller vessels. 
Secret Sub - USS Halibut
The USS Halibut started life as a guided missile submarine performing nuclear deterrent missions at the height of the Cold War. She finished it as one of the world's most secret submarines, performing covert missions close to Soviet shores including Operation IVY BELLS. For these operations she carried a new type of Navy Diver 
Naval Special Forces weapons quiz
A quiz which is much closer to the core of this website, the often exotic weapons associated with Naval Special Forces
IS-MIX advanced mixed-gas rebreather
There's very little information publicly available about the new IS-MIX rebreather, so here it is... 