Originally Posted by turkey_claws
Maybe sonar was the wrong word to use...
But bombers did have ways to detect enemy submarines that were close to the surface and close to them...
Sure. Its called eyes of the pilot.
As someone said, once RADAR was developped, they could detect snorkel and periscope at a point, but if the sub dove without anything on the surface, there was no way to detect them without a surface source.