When you surprise someone with a variation on a Wet Willy ... but instead of wetting your finger with your mouth, you wet it with your butt. And instead of putting it in their ear, you put it in their mouth.
Victim: "Oh, man... your finger tastes like crap!"
You: "Yeah -- you just got the dirty fish hook"
While making love doggy style, you stick 2 fingers in her asshole. Then remove the fingers and reach around to her face, in one swipe wipe her upper lip with your index finger "Dirty Sanchez". With your middle finger simultaniously hook the inside of her cheek "Fish Hook".
Did you see how pissed she was after I gave her the Dirty Fish Hook?
A close relative of the "shocker," however, it differs in technique and execution. Invert your hand and direct two fingers into the stink box, immeditaely followed by a thumb-hook to the stinker. You can also perform a "hooking" motion (like your twisting open a can) for the full effect.
If your girlfriend gives you the look, it's time for the Dirty South Fish Hook.
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.