This might be off-topic WRT the linked article, but I just wanted to take the time to say that I admire that you did this with your sons. If I become a parent I want to also instill the value of leaving behind a wake of improvement to our environment and communities, even if it's just picking up a piece of trash that would otherwise sit there until it decomposes.

So this is basically a shower drain hairs clog, except made up of fishing nets & lines?

I can believe that's heavy and hard work, hair clogs are already surprisingly difficult to get out & untangle (aside from being disgusting).

The tangle looks surprisingly clean though, are they mostly recent disposals?

It could be old. Rope doesnt break down quickly is why.

It's more buildup on it I would be expecting.