Although the Great Pacific Garbage Patch, which lies about half way between California and Hawaii, is infamous for the massive collection of plastic and marine debris going from the water’s surface all the way to the ocean’s floor, it is unfortunately not the only accumulation of human discard. There are at least 4 other gyres with marine debris throughout the world, one located in the Indian Ocean, two each in the Atlantic & Pacific oceans. In short, gyres are formed by ocean currents and wind patterns, amongst other things, which in turn swirl together various sizes of marine debris.
” …much of the debris found in these areas are small bits of plastic, or microplastics, smaller than 5mm in size that are suspended throughout the water column. The debris is more like flecks of pepper floating throughout a bowl of soup, rather than a skim of fat that accumulates or sits on the surface. Microplastics are nearly ubiquitous today in the marine environment and may come from larger pieces of plastic that have broken down over time, from fleece jackets or plastic microbeads added to [some] face scrubs.” 
“Floating at the surface of the Great Pacific Garbage Patch (GPGP) is 180x more plastic than marine life. Animals migrating through or inhabiting this area are then likely consuming plastic in the patch. For example, sea turtles by-caught in fisheries operating within and around the patch can have up to 74% (by dry weight) of their diets composed of ocean plastics. … Since 84% of this plastic was found to have at least one Persistent Bio-accumulative Toxic (PBT) chemical, animals consuming this debris are therefore ingesting the chemicals attached to the plastic.” 
“… at the NOAA Marine Debris Program, [they] focus on marine debris prevention and removal from shorelines and coastal areas where debris is easier to pick up. Prevention is key to solving the marine debris problem over time. If you think about an overflowing sink, the first step before cleaning up the water is to turn the tap off. That is exactly how prevention works. By acting to prevent marine debris, we can stop this problem from growing.
To prevent marine debris, we need to understand where it is coming from. It’s hard to identify specific sources, but we know that marine debris can enter our waterways and ocean in a variety of ways. Ineffective or improper waste management, dumping or littering, and stormwater runoff all lead to marine debris. If we want to “turn off the tap,” everyone, including government, businesses, and people like you [and I], will have to make some meaningful changes. We are the problem, and so we must also be the solution.” 
Sources:  https://marinedebris.noaa.gov/info/patch.html