They should be aware of this so either the projectiles the mob shoots with are rather slow or water related enchantments make you move faster in water.
At least I hope so ...
They just need to go ahead and like terra add in a no knockback item, enchantment, or potion or make a blocking sword reduce knockback greatly or kill knockback in the water. The idea that making skeletons harder to melee makes people carry bows was a really terrible one.
Nothing a skeleton ever drops short of a great enchanted bow is worth valuable arrows if you don't have a mob tower. I'd much rather save those for ghasts or killing blazes/nether fortress hunting.