Second World War submarines spent most of their time on the surface and moved slowly underwater, so aircraft could suppress their operations by forcing them to dive. German U-boats are described as lacking the submerged speed to leave through Gibraltar against the current, so an outward passage would require surfacing. That would expose the boat to enemy forces. One alleged German escape remains disputed in the discussion, with an Italian submarine proposed as an alternative identification from the timing. Italian submarine designers are described as having allowed for an outward passage through Gibraltar, unlike their German counterparts. A boat that reached the Atlantic still needed a base, and anticipated access to Spain depended on a political decision outside the navy's control.
Notable Point · 2:50:23-2:52:15
Why wartime U-boats struggled to leave the Mediterranean
German U-boats could enter the Mediterranean with the current, but their poor submerged speed made a covert return through Gibraltar extremely difficult.