PC user. Unable to start the frontiersmen mission "monster of the sea". I have finished any other frontiersmen missions, completed the main game, and any requirements to start this mission, but there's no symbol showing up on the map. I tried to find the travellers in the taverns of Boston but there's no way to start conversation there. My animus database isn't showing up "monster of the sea" and the frontiersmen mission is not completed so I'm sure I haven't played this mission.
So, you're saying you've been to the location it should be, but it's non-existent? I do remember that in the original ACIII, there was an issue where even mission markers wouldn't show up in places you'd never been & it's one of only a few games in the series where the viewpoints don't allow you to see everything, so you have to wander around & hope you get close enough to something for it to register on the map.
Usually frontiersman missions would be marked on the map once the prerequisites are met. I've definitely met the prereqs (full Boston map discovered, all other frontiersman done, main game finished), but this mission isn't showing up as it should be.
I checked videos online about this mission and no one mentioned having to find it first.
I play AC3 Remaster again these days, so I can definitely say that the frontiersmen missions are always in the same order.
The Boy Who Cried Wolf
Finding The Sasquatch
The Haunted Lighthouse
The Headless Horsemen
Monster Of The Sea
Unidentified Flying Object
The first four in frontier, the last two in Boston.
If you say you didn't play the sea monster, then you didn't play Unidentified Flying Object as well, because UFO is the last mission. And I read many posts about problems with the UFO mission. I play PC as well and had no problems with all these missions. Are you sure it is the sea monster mission, you are missing? I didn't hear it before.