I mean that's something that happens commonly when people fall into things like pools. When you jump into a pool you tend to take a breath before you do so, so you don't suck in water. When you fall into water it's much more common for people to aspirate or swallow water from the surprise.
Depending on a velocity, it also doesn't matter if you took a breath or not. Fall in quickly enough and at just the right angle (you can even do that from a fast water slide) and the water will be forced through your nose into lungs/stomach. (Unless you hold it closed)
