What tips does anyone have for stopping a dog from digging underneath a deck. This dog has a dog house at his convenience but would rather dig to get underneath my deck. Result is a muddy mess and he has gotten stuck a time or two also. Please help

Ih he is digging in the same place all the time you could try spraying something around the area that he doesn't like the smell of. Try to cosy up his kennel a bit too and give him a reward for going in there so he feels special for using it.

What breed of dog is it? Some breeds having digging in their blood which can make it harder to curb the behavior. How often do you exercise your dog? I noticed you said muddy mess, does this mean he only does it when it rains or does he do it at random?