This is a different time. Equestria blooms with riches from beyond the seas that used to be its borders. Nightmare Moon's disruption of the Summer Sun Celebration is an event that never took place, and the Elements of Harmony are only a Hearth's Warming chant. Discord itself is more of a spirit of bad luck than a conqueror, sometimes thwarting weather forecasts and other times turning fields into candy corn.
But Equestria also used to be free. Many took to the sea hoping to recover some of that lost freedom and, for a time, it was good. Pinkie Pie's Sugarcube was the most reliable sugar cane trading ship of the Thirteen Seas. Thanks to her, Sweet Apple Acres always had what was needed for jam, the Cake's bakery of Ponyville Docks was a booming business, and even her own ship's kitchen had the freshest muffins on land or sea.
Until the sugar embargo.
With increasing frequency, Her Majesty's navy has been keeping an ever closer watch on the trades routes.
They should have watched even closer.
(edit 2018-04-26: Probably safe to say this experiment is done.)