Here's my two-pennies-worth :
If less than 3 miles offshore nothing gets thrown/pumped overboard ... my one exception, being a keen fisherman & fish eater, is regarding food scraps/leftovers & veg/fruit trimmings, such material is chopped up & cast overboard as fish attractant/groundbait ... no harm in this since it is biodegradable.
When more than 3 miles out then I dispose of my garbage as follows :
Metal & glass, such as empty cans & pickle jars, overboard & made to sink not float.
Food scraps, paper & anything else biodegradeable goes overboard.
Plastic items are always retained on board then disposed of when next going ashore.
Sometimes, in an impish mood, it tickles me to launch a message-in-a-bottle ...