This may be an odd question but I am wondering if water speed affects a bullet's ability to penetrate water. Pardon my lack of knowledge, but I am aware that low caliber bullets can penetrate water past 3ft (Thank you Mythbusters). However, the tests they completed were all based around a pool full of water not running water, such as a river or dam. If I my understanding is correct, it is the density of water that causes the bullet to slow down, but does water speed affect this as well? Or would adding water speed the equation only effect the accuracy and not so much the speed of the bullet? I would assume that if water speed would indeed assist in slowing a bullet it would have to be a considerable amount of force in order to do so. Just to be clear I am a writer who is looking for some clarification for a potential event in a story, so mathematical calculations for my benefit aren't necessary. I would, however, appreciate some details so that the story can be accurate. There's just something fun about writing an interesting scenario that sounds far fetched but that could actually happen. Thank you in advance.