turns it it is nearly impossible to bomb/damage a dam just by dropping a bomb onto it - so a British enginneer spent his entire war time effort designing a bomb that would be dropped several hundred yards away from the dam, skip on the surface towards the dam, sink when arriving at the dam and then denotate at just the right depth- took years of trial and error to work it all out but he finally got it right and the RAF went wild blowing up germany dams
excerpt from DVD
"In 1943, the war was not going well for the Allies. The Nazis were in firm control of the European coastline and only approachable by air. Engineer Barnes Wallis had a bold (and, many thought, bizarre) idea to turn the war around. His creation--a bouncing bomb--was an innovative blend of simple physics and precision flying with the potential to unleash a torrent of destruction on Nazi industry. MAN, MOMENT, MACHINE details what happened on May 16, 1943, when 19 bomber crews embarked on one of the riskiest missions in WWII."
http://store.aetv.com/html/product/index.jhtml?id=74545