So I was in the fields outside Whiterun and there was this giant camp. SO I sneaked in and killed one of the giants with my arrows. The other began to chase me, and chased me all the way to this small stream to the left of Whiterun right next to the brewery. I crossed the stream as I was fleeing and shouting as my strategy, and for some reason the giant just stopped before the stream. It looked up, then down, then walked away calmly. I crossed the stream again to tempt it and it chased me, then stopped at the stream. It kept walking away and coming back and walking away again, which confused so much. I eventually killed it easily, but I never understood why exactly it did this. Do giants have a fear of water or something? Am I the only one to notice this?

I played again and it happened again. So I doubt it's my game glitching one time. Any ideas?

you'll find that most enemies pathing gets a little wonky around water. Bigger things won't cross, smaller things will sometimes look for a way around.