Iran operates submarines in the Strait of Hormuz and the broader Gulf of Oman. The fleet is not large, and the vessels are not modern by the standards of major naval powers. What they represent is a persistent underwater presence in one of the world’s most difficult antisubmarine warfare environments — a shallow, thermally layered, acoustically cluttered body of water where detection is genuinely hard and where even a small submarine with limited capability poses a disproportionate threat to shipping and to surface naval forces.