Figures. I bet you don't have holding tanks either.

And those who have them (the holding tanks ) usually empty them in
marinas........in the med that is.in the atlantic it s npot really
making any diffence anyway.......
But the antibiotics idea is a bit .........far for me.normal
antifouling on my boat ,has lasted 3 years so far ,but we keep in
river for 2 winters ,afloat.
Fresh water kills the sea thinkies ,and boat is always clean.now for 6
months in the med we dont yet have anything on the hull...it was 2
coats of international i bought in UK for 40 something quid.
your call but dont get the hull used to meds ,it might become addicted
and want more.....
g