The water mechanics are actually the biggest flaw in this game imo. Your essentially removing an entire potential biome with the way swimming works. We could have some underwater resources, foods, etc. There could be an entire set of armor made from serpent skin for example that could let you move more freely in water and while i understand not being able to use a giant mace in the water things like knives, spears and harpoons are all realistic choices.

I don't have much hope for any of that to change but i would think it should at least be possible to make a few weapons usable.