Submarine launched missiles

[Mach42]

(If this is the wrong place for this please move it)

Looking at the SLCM launch @ 0:20 in this video. I want to ask, how other countries make their missiles launchable from submarines?
http://www.youtube.com/watch?v=phhNtxhSKOg

 

[Sferrin]

Some have canisters, some don't. As I recall, the Sub-Harpoon and Exocet both have canisters. Subroc didn't. Tomahawk doesn't I don't think.

 

[Mach42]

Some have canisters, some don't. As I recall, the Sub-Harpoon and Exocet both have canisters. Subroc didn't. Tomahawk doesn't I don't think.

How are the ones without canisters modified for (or built from on onset) to be launched from underwater?

 

[Bill Walker]

From memory, most vertically launched ballistic missiles do not use canisters. They use some type of gas generator that creates a large gas bubble around the missile and ejects the missile clear of the water. The rocket motor ignites then, clear of the water and the sub. Try Googling for videos of Polaris or Trident launches.