I logged on last night and did two of the three shrines. Logged on today and all the deeds were saved, went to Belle, got the note, and finished the last shrine. I went back to Belle expecting to "Finish the Ritual" but it only registered me completing one of the shrines despite having the deeds of completing all three. As far as I'm concerned, this means one of two things: first, the adventure is bugged and it doesn't keep track of your progress. Second, it's working as designed (expletive deleted) poor design.
I cannot express how (expletive deleted) angry I am that this is the case. One of the primary motivations behind releasing sea forts was that they wanted "short, accessible voyages for crews with little time to sail to able to complete." They know many of their players have limited time, and the fact that the adventure doesn't save your progress is absolute horse (expletive deleted). I hope that this is a bug and it gets fixed (expletive deleted) soon.
Get your (expletive deleted) head screwed on straight, Rare.