In the article I was reading, the Germans had floating ack barges that they moved around to make it hard to find and destroy the barges. When they found them, they tried skip bombing but the ak fire from the barges was heavy I guess like trying to kill a B17 from its 6. The P-38s successfully sank the barges by dive bombing them instead of skip bombing.
From what I have read the fuse delay was the secret to a good skip bomb run.