I realize that a question about bolt firing from a crossbow is unusual, but it is still a piece of ammo. There is a cool Russian movie called “1612” youtube.com/watch?v=SQ_T8Lw_n8Q&NR=1 about a time in Russian history when a lot of people got killed for no reason (like it never happened again!). There is a scene in which a guy fires arbalette (crossbow) while submerged about 2 feet below the water. And he puts the bolt into a soldier’s face! Does that sound realistic? Can a crossbow do that? I know zilch about crossbows.
That sounds like a good one for Mythbusters. I have been wanting them to do more bow and crossbow myths, especially the shooting into and beneath water ones like they did with firearms.
I have studied about medieval/renaissance bows and crossbows to some degree, but don’t have any practical experience with them. My guess would be that the drag the water created on the bow, string, and bolt would make it rather ineffective. In any case, it would be a buggar to aim.