The more obvious answer to this scenario would be a to use a muskrat, a big one should just about fill up a 4" pipe, that would work for the pig and everything, might tie a rope around his neck so that you can give him a little assistance around the elbows and everything. if he didnt fit tight enough in the pipe to drag water you might let him lay in the sun for a couple hrs, he will tighten up good.
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