The quests recommended level is 7. Every time I am near the ship to get the supplies there are level 12 to 15 Blackbeard ships next to it, while being in a level 6-10 Undead Waters zone.
I believe the seed I use places the spawn point / route of the ships from the neighboring level 11-15 Blackbeard Waters zone too close to the quest target.
On different attempts I encountered everything from 1 level 13 warship to up to 4 level 15 ships.
Of course i could just be unlucky, but if that is intended behavior it should be reflected in the quests difficulty.