KingOfTheApes wrote

Well, there are islands on the water and the batteries are left behind
on the islands.

I suppose it's happened, but it darned sure doesn't happen often. Boats big
enough to carry batteries, don't work without them. They have to have them
to start the motors. It's really unlikely that anybody would go to all the
trouble to drive their boat out to an island with a spare battery on board,
change the battery while on the island and go to all the touble to take the
battery off the boat just so they can leave it someplace where it will later
have to be collected by another power boater. It could happne, but I don't
know why.

It's much more likely that any batteries you round were taken to the island
for use by somebody camping there. They may or may not have gotten to the
island by power boat, but the batteries you see almost certainly weren't
lift there because they are power boaters.

Well, maybe they heard of the coral reefs in the tropical waters of
the Caribbean dying because of all the pollution and motorboats that
anchor in the wrong places.

In more than 45 years of diving, and boating in the Caribbean, no, I've
never heard of it. I have heard of them dying because of fertilizer,
sewerage and other chemicals washed our from those on land who have less
consideration than either you or I do. I have heard of reefs destroyed by
sewage outfalls operated by Miami Dade, Broward and Palm Beach Counties. I
have heard of reefs destroyed by "accidental" leaks of millions of gallons
of raw sewage from Miami Dade about twice a year. I have heard of reefs
destroyed by those that dispose of thousands of tires as "artificial reefs"
that nothing ever lives on.

Here's a clue. Gas floats. Reefs don't. Anchors don't do much damage and
their use is not limited to motor boats. Sailboats and even kayaks carry
them too.

Lee