The U.S. Navy SEAL (Sea, Air, Land) Teams are a special operations force trained in guerrilla warfare techniques, counter-insurgency, and direct action. They are skilled, professional, and inside your nightmares.
The United States Navy SEALs are a group of highly trained and professional soldiers whose duties are typically based around guerilla warfare and counter-insurgency operations. For those of you who don't periodically curl up with a cup of tea and a book on military terminology, "counter-insurgency" involves attempting to defeat enemies who function less like a typical standing army and more as a stealthy, decentralized force that prefers small-unit tactics like digging pit traps, sniping, and spamming hadouken in street fighter. Most insurgent forces try to use the local population and terrain to their advantage, remaining effectively invisible while picking away at a more cumbersome and unwieldy opponent.
If that type of combat sounds familiar, congratulations; you've been reading far too much about ninjas lately. The astonishing thing about the SEALs is that they train specifically to fight forces that may as well be composed of black-clad japanese people with supernatural powers...and win because they do it better. In Vietnam, the first war the SEALs took part in, their kill/death ratio was enough to make a counter-strike fanboy drop his pants and sing the hallelujah chorus: 200 Vietcong died for every one SEAL. If you assume that the average weight of a Vietcong soldier was one hundred and forty pounds, that's 28,000 pounds of corpse, the rough equivalent of each dead SEAL taking an abnormally large African Elephant as a prop on his journey to the afterlife. These people are so badass that the theme from "The Good, The Bad, and The Ugly" plays every time one walks into a room.
Their training is just as terrifying as the SEALs themselves. On average, a SEAL spends over a year in training before they are even considered for certification - and this, mind you, is on top of whatever military training and experience they have before they enter the program. During their training, there is a three-week "Indoctrination Course," the first segment of which is nicknamed "Hell Week." The SEALs are literal-minded people; 70-80% of trainees drop out in that section, presumably because their chi-energy is unequal to the task of resisting the Satan's Nightmarish Palm technique. Since they are affiliated with the Navy, much of this training is based around amphibious warfare, including proper diving techniques and selection of landing sites. Additionally, they are trained to resist environmental extremes, especially freezing temperatures.
As if this were not enough, the specific skill sets they learn during their training are even more impressive. One of these is known as "Surreptious Entry (Mechanical and Electronic Bypass)." Good luck with that alarm system; if you're lucky, they'll laugh at it for a couple of minutes, giving you the opportunity to compose a witty epitaph before they sneak through the ventilation ducts and headbutt you to death.
They also have "Breacher (Barrier Penetration/Means of Entry)" which is presumably used when stepping into the spirit world and hunting you in your dreams just isn't fun anymore. In layman's terms, if you mess with these people, they can blow down the walls and take you apart like you're an extra in a Tony Jaa movie.
And finally, there is "Advanced Special Operations." God only knows what these people consider "Advanced." Psychic Warfare 101? Angel of Death Studies? Bughunting?
If the SEALs ever meet Xenomorphs, it may be wise to bet on the winning team.
After all - they are professionals.