Terrapins are semiaquatic animals, living in our dams and marshes and have a preference for stagnant water. They are also omnivorous which explains why this little guy ended up swallowing fishing line hook and all. 

It’s highly likely that he made a meal of discarded / broken fishing line with a baited hook.  Admitted with the fishing line protruding from his mouth, an on-site x-ray showed the hook firmly lodged in his digestive tract.  The hook had unfortunately caused too much internal damage and this terrapin succumbed to his injuries.