An aerial torpedo can descend below its intended running depth after entering the water. In a shallow harbour, it can strike the bottom before coming back up. American, Japanese, and Italian practice is described as adding wooden fins to reduce the angle of entry, although the initial downward movement remained. The British tension-wire method forced a flatter, belly-first entry. The comparison explains why adapting a torpedo for an attack in harbour required attention to its initial plunge as well as its eventual running depth.
Notable Point · 54:23-55:38
How aerial torpedoes were adapted for shallow harbours
Wooden fins and the British tension-wire method reduced an air-dropped torpedo's dive, making shallow-water attacks more practical through different solutions.