Early homing torpedoes worked but were spoofable

How effective were the first homing torpedoes used during the Second World War?

They had a real effect but took time to mature and were easier to decoy or confuse than popular portrayals suggest.

Second World War homing torpedoes had an operational effect, but their guidance took time to mature. They were easier to spoof than film portrayals suggest. One report tentatively describes a torpedo spending its time chasing itself. The anecdote remains a reported possibility rather than a firm description of how every early homing weapon behaved.