I don't think, for example, that cruise ships are allowed to dump their shit (and other refuse) into the sea, provided they're in international waters.
Depends where they're registered. The vast majority of countries have signed on to the conventions forbidding dumping, and can enforce it on ships flagged in their countries, but a seastead intending to dump would presumably not sign on.
"Carnival Corporation ships illegally dumped more than 500,000 gallons of treated sewage, 12 gallons of oil, 11,000 gallons of food waste & dozens of physical objects into the ocean during its first year on probation (4/17-4/18)."
The large list of incidents have inane stuff, some human stuff, some funny stuff and some ironic stuff all mixed in with very serious stuff. You have to pick through a lot of entries and text to make sense of it.
Empathic: "While the ship was alongside in Mahogany Bay, Isla Roatan, a passenger accidentally dropped her purse into the sea from the pier. The MARPOL Annex V violation was reported to the port authority."
Funny? Inane? They had to file a report anyway: "During loading of provisions in Galveston, Texas, a shore side worker placed a pallet of watermelons on the ship's platform. Due to the pallet not being correctly positioned on the platform, the pallet tilted causing a number of watermelons to fall. All the watermelons were recovered from the netting placed below the ship's loading platform."
Ironic: "While alongside in Galveston, Texas, as a passenger was boarding the ship, he dropped his paper boarding pass, which was blown overboard and into the water in violation of MARPOL Annex V. The Harbor Master was informed by the ship's local agent. No additional actions were requested."
Serious: "Approximately 467 cubic meters of treated black water/sewage and 6.2 cubic meters of comminuted food waste was discharged inside Bahamian Archipelagic Baseline between June 13, 2017, and June 15, 2017, due to misinterpretation of Bahamas baselines listed in ENV 1001."
