Leonardo da Vinci proposed a double-hull ship design intended to improve protection against damage and flooding.
The concept placed an additional layer of structure inside or alongside the outer hull, creating separated spaces that could help keep water from spreading through the vessel. Leonardo’s notebooks contain ship and naval-engineering studies showing his interest in hull strength, buoyancy, and compartmentalisation.
A double hull is not the same as a catamaran. A catamaran has two distinct hulls joined by a deck, while a double-hull vessel has an inner and outer hull surrounding a protected space. Modern tankers use double hulls mainly to reduce pollution after a collision or grounding, but Leonardo’s historical proposal belongs to an earlier military and maritime context.
Leonardo did not invent the modern steel tanker. His drawings were exploratory designs, and surviving evidence does not show that this particular ship was built and tested as a working vessel.