Tons of plastic waste ends up in the ocean, with the bulk coming from China and Southeast Asia. However, the concern with straws is the harm they cause to local wildlife at their macroscopic sizes.
Throwing it in a bin reduces the amount of trash that ends up in the ocean, but wind, homeless, gravity, can all result in trash ending up outside of the bin and on a path into the water.
Tossing out "homeless" for a reason trash ends up in the ocean really undermines your point and makes you seem like an asshole. Maybe I'm naive, but I've never seen _anyone_ intentionally take things out of the trash and toss them somewhere else. I can't imagine this happening (caused by any human) on a scale where it is worth mentioning before mentioning negligent littering.
Sarcasm aside, metal straws don't float, and fish and birds don't try to eat them. And unless you have some fancy expensive metal straws, in a corrosive sea salt environment the ones generally available rust in a matter of years.
Bioplastic straws are a superior solution.
Compostable straws can be made of bioplastics, but require high temperatures to biodegrade, meaning generally temperatures not found in nature (outside of volcanic areas).
No, they're not. Full stop. It's not just the production of the straws that matters, it's their post-use effects. They can choke birds and fish, pierce stomachs or guts, and eventually become microplastics that get eaten by plankton and fish since the plastic doesn't degrade on a timeframe relevant to human or even generational lifespans.