Burnside was an idiot. Consider the following:
At 10 a.m., Burnside had split his troops. One division is sent downstream to cross a ford. The rest stay behind to storm the bridge.
Crossing the bridge proves to be a monumental task. On the other side are about 400 Georgian sharpshooters posted atop a steep, wooded bluff. They are backed up by a mere 2,000 rebels who distance themselves from the bridge.
Although Burnside's force outnumbers the Confederates more than 5-to-1, it takes three hours and two disastrous assaults to finally cross.
How many Union troops were killed trying to cross a narrow bridge over Antietam Creek, which was about a foot deep?
Was Burnside afraid that his troops would get their feet wet?