Why does Early think Fisher is alive?

There were nine men in Fisher's squad, and they were trying to blow up a bridge. The Germans were coming from the north side. The shed that was blown up was on the south side. One man had to swim the charges across the river and plant them under the bridge. Early believes that Fisher would have volunteered for the mission. He would have removed his dog tags so they wouldn't make a noise or reflect in the moonlight. Then he would have swum underwater to avoid being seen. Since Fisher was in the water, he wasn't hurt when the German bombed the shed where his squad waited.