Where's My Black Flag Achievement/Trophy Guide
This achievement is a little time consuming but can be done quickly once you hit level 28. There are 9 ships in Assassin's Creed Origins that count for this achievement and will usually do circles of the specific region that they are in. In the following video I showcase the locations of all 9 ships then attacking one.
The following ship locations are:
Mesogeios Sea - 1
Great Green Sea - 1
Lake Mareotis - 2
Im-Khent Nome - 1
Ineb-Hedjet Nome - 1
Atef - Pehu Nome - 1
Faiyum - 2 (Okteres Bloackade doesn't count.