An aluminum hulled boat, designed as a transport.
In the Navy while on the USS JFK CV-67, I was amazed at the ship's construction. All that steel looked pretty thin, supports at 3/16" to 1/4"...until I had to drill some of that hardened armor plated crap with an electric hand drill.
Then I toured the USS Iowa and thought "Wow, my ship is built like a cardboard box."
Then I got a guided tour on a USNS cargo vessel. I thought "This thing is built all kinds of flimsy."
Fast forward to a couple of years ago and I went on my first Carnival Cruise. I thought "This thing is made of glued tissue paper and going to rip open!"
The USS Stark was a combat frigate, made of aluminum. It isn't the most durable, even when built for combat.