Leonardo da Vinci proposed a double hull to help prevent a vessel from sinking.
Leonardo’s ship designs included an inner hull protected by an outer hull, creating a space between the two layers. If the outer skin were damaged, the inner structure could remain watertight. This is the same broad safety principle later used in many modern ships and boats.
The idea was especially relevant to naval warfare, when collisions or deliberate attacks could breach a vessel. Leonardo also explored ways to improve ship construction and maritime machinery, showing that his notebooks covered practical engineering as well as artistic studies.
A double hull does not make a ship unsinkable. It can reduce the risk from certain kinds of damage, but flooding, structural failure, or damage that penetrates both layers can still overwhelm a vessel. Modern double-hull tankers became especially important for limiting oil spills after collisions, while Leonardo’s proposal belongs to an earlier period of experimental naval design.