Why Vian blamed his hesitation for HMS Naiad's loss

A screening destroyer spotted a surfaced U-boat but used a dim shaded signal that took time to reach the flagship. Seconds remained when the warning arrived, yet Vian hesitated when Captain Grantham asked which way to turn. In Vian's assessment, an immediate alteration of course would have moved the hit into one engine room instead of the bulkhead between both rooms. Flooding spread into the boiler rooms, and Naiad capsized within minutes. Grantham worked on saving the ship and organizing abandonment until he entered the water without a life belt, then helped non-swimmers reach rafts without taking their scarce space himself. Vian blamed his own hesitation and recorded Grantham's rescue work.