Dog not crossing water!!!

Just my .02 but I think the dog just lacks the confidence to cross.the water. When he is on track or going to a bay he is not thinking about the water, all he knows is that there is a pig on the other side. Rough handling ( dragging behind a four wheeler, jerking him in and through the water, throwing him in the water, etc.) of the dog is probably not going to help him, it.will more than likely make it worse. You already said that he will cower down when you go to get him. He is obviously associating the water with something bad happening to him and by doing the things you have tried it will only get worse. Try the squealer and just take your time with him. I know it sucks but if he is.as good as it sounds he will be worth it. No dog is perfect, just consider this his bad habit and work through it.