A troller with fish nets ...

A troller with fish nets might work.  You would have to use floats on the nets to keep them at the surface, but they could cover a large area fairly quickly. The best solution is to keep the trash from getting there in the first place. Many coastal communities haul their trash out to sea and dump it. This practice needs to stop. I remember in the seventies watching the barges in New York City hauling out huge loads of trash to sea. Of course, any floatables would wind right back on the beaches. Land fills are the best solution to this. Our oceans are not a dump.