What materials were submarines made up of?

Submarines are primarily constructed using high-strength steel, particularly specialized alloys that can withstand high pressures underwater. In modern submarines, materials like titanium and composite materials are also used for certain components to reduce weight and enhance durability. Additionally, pressure hulls are often reinforced with various coatings to prevent corrosion and improve longevity. Some advanced submarines incorporate advanced materials to reduce their acoustic signature for stealth purposes.