What's wrong with this picture: Plumbing P Trap

ANSWER:  Improper sink trap.

It appears that a do-it-yourselfer may have gotten in over his head. This homemade sink trap constructed with corrugated plastic does not serve its proper function, as there is no actual trap, and waste gases could potentially seep up through the piping and into the room. It is also easier for objects to get stuck in the corrugated plastic material. This sink should be repaired by a licensed plumber, who will install a modern P trap with PVC piping.