[lugoues]

I thought they just dumped it overboard but maybe there are some ethical cruises... maybe.

[idlewords]

It's fine to dump sewage overboard if you're far enough from shore. Cruise ships treat it to some extent, but ultimately it all becomes fish food.

[euroderf]

In the same way that every breath you take contains at least one atom-or-molecule of Caesar's last breath, every sip you take contains at least one atom-or-molecule of every cruise ship waste jettison. (Assuming sufficient worldwide diffusion time.)

[mannykannot]

It seems that in most ports they are required to hold and treat it (and, perhaps to a lesser extent, in inshore waters.) Fouling the places they take their customers to is ultimately bad for business.