Summary: Naval instructional film using graphics to illustrate some suggested anti-submarine tactics.
Description: A convoy is guarded by escorts arranged in a half-moon, with one vessel keeping station astern. The formation re-deploys to permit one vessel to break away to intercept a U-boat detected by HF/DF. The U-boat dives and the escort drops depth-charges at the "datum point" of submergence before searching with asdic around the "furthest-on" circle. Contact is renewed, but the film does not indicate whether the submarine is subsequently destroyed.
