In this judgment, likely following close on the heals of the grievous sores of the first bowl judgment, will see all the oceans of the world turned to blood, killing everything in them. The water will literally become blood, and thus undrinkable. But what's even worse is that shortly after this they will begin to rot, as will all the corpses in them, causing a stink so bad as to be nausea inducing on an incredible scale. Those who are saved during this time will not be affected by this, but anyone who has the mark of the beast, and perhaps those who are yet unsaved, for whatever crazy reason, will have to deal with this, and it won't be pretty.
Also, this will have the secondary consequence of further reducing the world's food supply by killing off ALL sea life. Literally the tuna, the crab, the sea birds, the turtles, and anything that relies on the sea will die. ALL OF IT. So not only will people struggle to find potable drinking water, they'll have to contend with this new shortage of available food which will be added on top of the already massive shortages that will exist at that time due to other prior judgments.
(*Do you have a better description, or did you find an error? Please let me know.