I've thought about this idea for a long hard time. as I am from of Caribbean decent. I thought long and hard about the absolutions of the dead eye world. and I know this.
water contains hydrogen, and in my world hydrogen is a substance, used in white magic. or holy magic, is why water will eventually dissolve most things.
So I thing if this powerful substance Is in the bases of water what will it do. how will it react to magic in such a fictional world. And as hydrogen atoms contain the power of nuclear bombs. I figure this.
water is a magically endowed substance. And when used in magic, is the best thing for stopping or diverting, magic and dispersing it quickly. much like how chi works.
if a boat that is magically endowed to resist magic. then in a ocean it would constantly be getting drained of this magic. especially when the water is enhanced bye salt. it would expend its magic ability so fast that it would eventually start to degrade within the property of water. as once put in water the magic would begin to disintegrate the boat as even magic comes with a price.
Water magic. as it is so rarely used only works when one replaces the hydrogen atoms of a water molecule with their own magic. meaning it is barely water at all. and more like a venom of sorts as when magic is applied, it turns to a water like poison. as is why something that would usually Bering life. becomes so deadly.
It true that some can make enough water magic to move entire oceans. or streams or lakes. witch is why however it is so redundant.
as when a single drop of water touches magic water, it will crystalize. and turn into magic crystal, before turning into a giants water backlash explosion, hurting all in the vicinity.
Depth charges can be made with this. and though it isn't technically water being moved they can be big enough to cause massive waves in oceans and lakes and so on. as is why water magic users like to keep their own container of magic specified water sealed away.
water can even be used bye some guns as bullets. but is takes some time of concentration to actually turn water into magic water. witch is why it is such a scarce magic type. outside the dead continent. or otherwise. \magic water can be compressed however to that large amounts can fit in small containers.
merchants make a living off selling this item. as pre magical water is easier to change over to someone else's magic type.