Giant Plastic Island: Fact or Fiction? by Tom Hartsfield answers my question about the trash island. You wouldn't know that you were sailing through a trash island unless you were paying exceptional attention. That doesn't mean we shouldn't do more to control runoff and pollution. All it means is that we have to be more careful about the stories we tell, no matter how good out intentions.
So, here are the facts. Much of the ocean contains little to no plastic at all. In the smaller ocean gyres, there is roughly one bottle cap of plastic per 50 Olympic swimming pools' worth of water. In the worst spot on earth, there is about two plastic caps' worth of plastic per swimming pool of ocean. The majority of the plastic is ground into tiny grains or small thin films, interspersed with occasional fishing debris such as monofilament line or netting. Nothing remotely like a large island exists.