With the basic idea "All small streams become a big river", can't you hang plastic catching nets after cargo ships?

 

The net would then be closed when it was full and then in port a tugboat would take

over the tampers  and pull it to the place where it was handled. 

There are ships that pull plastic catching  nets behind them but then pick it up on the ships,

 but if many cargo ships could catch a few tons per trip, it should be a considerable

 amount in total that was caught and significantly more than these cleaning vessels can achieve.

https://youtu.be/T2FNqfpdHV8?si=NP6iHga0YykbOqQV

 

Then, an ultra/infrared sound that scared away fish and other animals in the water in front of the ships, so a lot of bycatch was saved.  The ships could get compensation for the extra fuel consumption or tax credits where some could arrange a winch so that the net was raised a bit towards the stern/side and possibly with the right winds have an extra sail that could be folded out/in quickly, which everyone could invest in already now for saving fuel.

 This and better handling of garbage are two ways to go, as the more micro plastic, the more environmental impact.

https://thepremierdaily.com/plastic-bottom-at-of-mariana-trench/?57vm=dzjz5o