When I was about 14 yo I paddled my pirogue up into a shallow area to try and get into an old cutoff. It was spring high water so this area was normally dry(ish). I parked the pirogue and went into the ankle deep water to try and scout a passage and I had my trusty Crosman 140 .22 pumper. About that time I heard some noise from the other side of some willows and so snuck around to see what it was. It was a group of feral hogs.
At this point I was on dry ground, my pirogue about 50 yards distant parked in some rushes and cattails in shallow water. Hmmm, I picked out a nice size one, put the sights on the head behind the ear and pulled the trigger. They all jumped at the pop but not seeing me hidden in the willows and brush went back to feeding. The one I shot just snorted, shook it's head and continued on doing what it was doing. I pumped up again as quietly as possible (not easy) and shot it a second time, all H and e and double L broke loose. Pigs were running all over, squealing, snorting and then all of them including the one I shot came to be heading in my direction. I took to running and somehow lost my rifle. My feet were walking on water and I got in the pirogue and pushed into deeper water of the bayou just in the nick of time to not be eaten by the frenzied hogs. Then realized, my rifle was left behind.
Forlorn I returned home whereupon my grandfather asked me about where my rifle might be and did I not have any squirrels to clean? Upon telling him the story, first his face flushed, then turned bright red and then with much arm waving and some curse words I was told that a southerner never drops his rifle and runs and we are going back for it NOW! He grabbed a 12 guage and off we went to retireve my Crosman. Well, the rifle was on a patch of reeds, mostly dry and aside from a stain in the bluing was no worse for the happening. No pigs to be seen. My grandfather did not speak to me for days, dropping your rifle and running, what are you some sort of yankee or something! It took a lot of squirrels to make up.
So, no, no, a .22 air rifle is not enough gun for a tough old hog. Or any hog for that matter. But you can try, best have an escape plan or a pirogue nearby. The damaged bluing can be seen here, kind of dull area with no sheen where it laid upon the wet reeds.