uuurr watch the news
besides needing to pass a very high standard of physical training, an out and out fascination with war may not be a required attribute.
you obviously do not not know what up shite creek without a paddle really means
To gain a good insight into current ops, selection and training have a perusal of the aptly titled royalmarines.uk forum. There are a good number of currently serving trained ranks able to give you a few pointers.