Of course you wouldn't.
But that, in effect, is what all of us have done with our plastic trash that ends up in our oceans.
Two points here.
1. The ocean IS our backyard. I'm sure you've heard the phrase "sea level." Everything higher in elevation than sea level (everything on land) is pulled by gravity towards sea level. Some things move faster than others, plastic bottles move like a bobsleds towards sea level while your car stays put. You wouldn't throw trash in your backyard so don't throw it anywhere else that will end up in your other backyard... the ocean.
2. Rise above plastics. All the plastic trash you see in the image to the left was used for maybe... ten minutes. It will last for tens of thousands of years (arguably forever). What's worse, a grotesque amount of our everyday plastics end up as ocean trash. Every beach on the planet (that hasn't already been cleaned up) has plastic trash on it. Check out the 2 minute video below I shot in the Maldives. For some perspective look where the Maldives are located... they are far away from... everything. Yet the mythical deserted island is inhabited... by tons of plastic.
Become vigilant about refusing plastic water bottles and single-use plastic bags.