What Happens to Plastic in the Ocean?

As they say, the first plastic bag ever made is still floating around out there somewhere. I am not an eco activist, but yesterday at the grocery store they told me they had no paper bags, only plastic. I surprised myself by thinking, this is a big enough deal for me to switch grocery stores. I mean, we have the choice and we know the consequences, and still we are willing to pollute the oceans so the grocery chains can scam us for another buck on top of what they are already inflating their food prices for? Because to add insult to injury, they CHARGED me for the plastic bags. (I know, I’ll bring re-usable cloth bags with me next time.)