Actually my dive partner found a 45 with a silencer on it off New Jersey.
As for trash or garbage, that in itself won't hurt a reef or cause any bleaching. Of course if a piece of trash is laying on a coral, that piece may die, but the coral will just grow on it. Here in New York I have been diving for lobsters since about 1974 and the main place we find lobsters in in tires. Almost every tire has a lobster. On bare areas with no trash or rocks, there is nothing.
Also under the many bridges we have here the bottom is filled with construction debris. Again, loaded with lobsters.
Some "trash" in some places is advantage to sea life. Not chemicals of course. But here in NY at least which is not reserved as a divers paradise by any stretch of the imagination I have been asking for areas to be put aside to fill with tires as a test. The only thing that limits lobsters here is lack of living places. The Sound is almost all rocks but only one lobster will live in a hole and it will chase any other lobsters away so we need more holes.
Also fish do not spawn on open sand or mud, They lay eggs in tires, bottles and cans.
I am only talking about northern waters like NY, not the Caribbean, Tahiti or Hawaii as those places depend on tourists, but even in those places they could place cinder blocks or pipes in areas that divers do not go just to provide breeding places for fish.
The fish in my tank spawn in the bottles more than in the rocks.
My copperband disagrees.
I salute you for daring to dive around here!
To your point about trash reefs, the MTA used to dump subway cars in hope they'd become artificial reefs, the Pentagon dumped tanks and all sorts of gear, off the coast of Florida there were attempts to make tire reefs. See article below how one turned out - other sites remain. Agreed that nothing grows in mud etc but as it turned out those projects were all abandoned after most inexplicably crashed following a short boom. Some theories as to why indicate very poor biodiversity, insufficient to support a reef, but we don't fully understand.
http://www.latimes.com/nation/la-na-florida-tires-20150524-story.html