That problem existed indeed and was taken head on by the cruise ship industry.
Nowadays on the modern cruise ships (the few I was on) the waste management would make any small USA town proud to have.
The waste, gray & black-water treatment is even for the extreme high Austrian standard perfect
(we have in Austria probably the best water in the world - most comes from ancient glaciers)
as it releases basically no pollution worth mentioning or being afraid of behind.
Multistage cleaning, including large bacterial ponds to break down the last remaining chemical debris I have seen on board
the leading MCS cruise ships
MSC Cruises | Beautiful. Passionate. Italian.
Cooking oil from the kitchen leftover is separated, processed and added to the ships fuel - burned in the ship diesels.
Waste which cannot be processed on board is sealed, cooled and discharged from ship in the port to be incinerated.
Cruise ships are a easy target (commies "kill the rich") and political proper to criticize - especially for many private and state industries and investors special interests, having the intention hiding the real imminent dangers on the seas - and their involvement
Its not a pipi of a old lady on a cruise ship, folks,
the world will under. e.g. the way of the
Studebaker, GM & Chrysler -
the globe can take that little pipi without blushing.
So my dear TEG - Dont insist stubbornly on things you know from hearsay of third parties only - because you dont like me for trashing your perfect little world with solid & hard facts of real life.
The real destroyer of the worlds seas are the countless offshore drilling platforms, nuclear industry, plastic bag industry (the most beautiful Italian coastline - the Amalfi coast above Napes is a stinking huge pile of extremely slow rotting plastic & bags - whole parts of Sicily are covered with industry discharge as far as from BG carried on by train already) and plastic lobby, oil-tankers.
The illegal dumpster industry earns the Camorra, Ndraghetta & Mafia (dumping waste from vessels and especially dangerous one by planes into the sea) more in semi-illegal net income then heroin & prostitution combined.
But on the seas especially the nuclear driven US military vessels, ships, aircraft-carriers and the submarines all in all ruthless plundering mother nature in many ways and far fiercer and for aeons to come.
Military ships go often with many times the folks on board a modern cruise ship has- not giving a rats ass for environmental footprint.
The army (their contractors are tripling that figure and are even worse) is leaving radiation and other extremely dangerous pollution behind and in front, our next generations to come will have a hard time to break down and survive.
No more bomb-making, but lots of work nonetheless
The damage done by military today remain so long stressing in the future our environment and will continue giving the US moral standing in the world a very sour touch,
even G.W. s pollution of the world would be forgotten by the time the leftover poses no harm anymore...
...and thats a very, very long time.
So my dear friend TEG - to conclude:
In contrary to a cruise ships little old lady's very personal absolutely ecological friendly and full degradable footprint (her little ****)
stands the poisonous militaristic industrial Tyrannosaurus Rex leftover. Piling and stinkin skyhigh.