Modern tankers have double hulls, to avoid (or trying to avoid) disastrous oil spills in case of accidents. In addition to other strengthening measures. Quite t

Modern tankers have double hulls, to avoid (or trying to avoid) disastrous oil spills in case of accidents. In addition to other strengthening measures. Quite the opposite of built as cheap as possible. Warships, on the other hand, are often built for speed, and something has to give. I remember visiting a (smaller) warship once, it could reach 40 knots, and it had a normal hull (not a catamaran or trimaran). The crew said the whole ship was made of very lightweight material.