Submarines are equipped with their own escape sets to allow personnel to leave the submarine without external assistance using an escape chamber or compartment.
The image below shows an older Mk9 Escape Suit.
RFD Beaufort Limited in Birkenhead have been supplying submarine escape suits to the naval forces of the world for decades, now part of the Survitec Group, they continue to enhance the ‘state of the art’.
Describing them as a suit is underselling them because, with the advent of the Mk10, RFD Beaufort integrated a single person liferaft and extensive hypothermia protection into the design
The Mk10 has been in service with the Royal Navy for many years, the image below shows a US Navy one on the surface, although the BFA (now Survitec) Solandri
The Mk10 equipment has been replaced in the Royal Navy with the BFA Solandri system from Survitec.
The system is designed to sustain the wearer on the surface for 24 hours and includes water, emergency rations, heat packs and signalling equipment.
The Astute class submarines have a two man escape tower called the Logistic Escape Tower (LET) aft and a Forard Escape Tower (FET), not surprisingly, at the pointed end!.
In 2012 both were validated during an exercise, click here for more information.
Every submariner must pass the escape course.
The Royal Navy has a 30m Submarine Escape Training Tank (SETT) at Gosport, an impressive installation.
Pressurised escape training at SETT ceased in 2009, the Royal Navy taking the decision in light of the emerging submersible rescue vehicle capability and an examination of risk, although other naval forces continue to maintain pressurised escape training facilities. All diving ceased at SETT in 2013.
By accident (honest) I found this video of the fetish scene making use of a RFD Submarine Escape Suit (safe for work link), of course, when you spend your working day in tight trunks and a dressing gown, one can understand!
Self-escape is the least preferred escape option and would only be carried out in extreme circumstances such as on onboard fire, total flooding or radiation leak.