[RPG] make infinite ice arrows using the Shape Water cantrip


I was thinking about what the possible uses of the cantrip shape water could be, and I realized that it might technically be possible for you to make infinite ice arrows.

Would this work? If so, what damage would something like this do?

Best Answer

Physics says no.

If we want to get all science-y about it, arrows have to be flexible. It's known as the "archer's paradox" -- an arrow goes where you aim it at full-draw even though it seems like it would have to go through the bow's body to do that. The reason is the arrow flexes back and forth as it flies just after release, rather like a swimming fish, and that's caused by the arrow actually bending around the bow; you can see this in slow-motion videos of archery (or in Disney's Brave).

Selecting the proper arrow stiffness, or spine, is critical to getting good accuracy out of it. You have to match the arrow's spine to the draw weight of the bow you're shooting with, among other things -- and this is in fact one of the most complicated parts of archery. There are dozens of variables involved in shooting with a compound bow that all affect how much spine you want. Too much spine or too little can both introduce random inaccuracy into the shot. (And of course an ice arrow would likely shatter under the launch forces involved in firing it.)

But this isn't physics class.

Since when do we let real-world physics tell us what to do? This is fantasy! We have magic! There's nothing in the rules of shape water that would stop us from making arrows from ice.

As a DM, I'd probably allow this because it's clever, and I like clever, but on the other hand a cantrip really shouldn't be a replacement for the time-consuming skilled craft of arrow-making (properly called fletching). This is a good emergency measure, but shouldn't be your everyday source of ammo. I'd probably apply disadvantage on the attack rolls, as the arrows aren't properly flexible, aren't as hard as a steel arrowhead, and are potentially misshapen (due to production flaws, melting, and so on). I'd also rule they can't be recovered because they shatter on impact.

Alternatively, a DM could treat the arrow as a generic improvised weapon, but that gets a little weird because generic improvised weapons can be thrown but there isn't a rule for using them as ammunition, so it's getting pretty far into houserule territory.