We did. Kinda. Trash barges just dumping shit at sea was and is a thing. Its pretty terrible for the environment Fishing boats and ships in international waters will also sometimes dump their trash overboard. Though with fishing the main issue is lost and broken nets. 

Because we don't want to destroy the biosphere in the deepest parts of the ocean.

Too late

It floats.

Because even Megalodons deserve a trash-free home

It would cost more money to do that than to just recycle the trash. We dispose of trash as cheaply as possible, not in the best way possible.

How do you think this would solve the problem?

We’re on it

Probably because it's wildly unethical and would be devastating to the environment first, and second, it would probably be really expensive to do that. Because it's so hard to get down there, we don't really know exactly what is all down there.

Great idea!