Suspiciously low?

[roverhi]

These drug interdictions at sea are almost always because someone dropped a dime on the enterprise or intelligence/police work before the boat left its loading point. Easy to get cooperation of a foreign government to allow boarding and seizure with that information.

Have heard that even the drug supplier will turn in unaffiliated smugglers. The supplier gets the money, the loss of the goods puts upward pressure on the market for future sales and they make out on the value of the next shipment. It's no longer a business for the independent contractor/entrepreneur.

[SeaSiren]

Satellites can and do measure the ocean surface to centimetre in height variations. So, it is more than possible that it was being surveyed.