You have the edges on point *cough* to better explain Fishman Karate, you should see an application of the same.
The old, but still capable senior looks the other way and preforms a simple palm thrust forward. At plain sight, it has no virtual motive or target, however a tree standing 5 meters away is suddenly blown back into the horizon.
Did you catch that? The essence of Fishman Karate is controlling all the "water" in your direct vicinity. From the water in the atmosphere to the body in one's body, the shockwaves propagate and go through them. Thus, even if someone has an "Iron" body, in which all forms of physical contact are useless, FK will play effective against this defense, as it's a shockwave that moves through the water within any human or anything composed of water.