It's interesting to me that you think the point of greatest effectiveness is exactly where I'd say realistically all hope is lost, the oceans being so vast of a surface and volume. This is end-of-pipe thinking where I believe we should really start at one of the many points earlier in the process: industrial consumption of materials and industrial waste management are such points, and as you say protection of waterways from pollution. Given how lousy mankind has proven to be when it comes to collecting and effectively re-using plastic waste while avoiding concomitant pollution of water and air and material down-cycling, the real mistake lies in the sheer enormous tonnage-per-year and its growth of plastic. This volume of production should have never happened in the first place. But of course it has so there's a place for ocean cleanup efforts. But to state that "the best investment [...] would be automatic cleanup mechanisms" while denigrating research efforts to produce better plastic-ersatz to me sounds like futuristic techno-boondoggle-babble, not unlike that crazy 'hyperloop' thing. Automatic ocean cleanup robots! Yaay! LA to NY in under 30 minutes! Yaay! Colonies on Mars! Yaa---wait wot?? People can't even cleanup after themselves or avoid throwing their trash into the next river, but no problem, we'll clean that up in no time AUTOMATICALLY?? C'mon give me a break.