I am thinking of a fish like a catfish, that swallows stuff whole. Catfish also swallow rocks and then later spit them out - presumably behavior like that is why it got the whole log cabin.
I have wondered how animals that swallow stuff whole get away with it. Especially things like scorpions that can hold their breaths a long time. The answer is that a stomach is a bad place to be alive. Strong acid and enzymes, muscular action rubbing stuff around (and up against rocks), no air.
The log cabin is the hope for your guy. The logs will hopefully hold up against the grinding and rubbing, and won't immediately be eaten away by the acid. The cabin will hold enough air for him to survive a while. A fish (or anything else) that eats stuff that proves indigestible (like rocks, or log cabins) will eventually puke it back out.
There will not be much of a view out the window. It will be very dark inside. If he understands his situation he will refrain from making a fire because it will consume the air.
