Not only are ALL 92 naturally occurring elements present in sea water, so is a trace of plutonium. Probably leaked over the decades from the various nuclear facilities that use it.
There are all kinds of bacteria, some unknown to science.
There are dumped, dead fish that are the bycatch from the trawlers.
All sorts of biomatter, including invertebrates too numerous to mention.
There IS raw sewage in the world's oceans.
There are all the chemicals used in chemical warfare as well, plus more ordinary explosives and munitions
All sorts of algae that can make you sick.
It is still full of industrial toxins. Any farm runoff into any river or lake eventually makes it into the ocean.
And then there is the issue of plastics.
It's a slow process but the UV light in the sun eventually breaks plastic down to microbeads.
We are still not sure what the impact of the microbeads is. Suffice it to say that no good has come from them so far.
All in all you CAN"T POSSIBLY know what you are getting yourself into by injecting raw, or even strained sea water into the body.
The US Navy now equips all it's surface ships and submarines with steam distillation facilities to create potable water for the crews.