Achievements:Accomplish the indicated achievement to get the corresponding 
number of Gamerscore points:

Heroes Aren't Born (10 points)     : Complete memory sequence 1.
Good While It Lasted (20 points)   : Complete memory sequence 2.
A Pirate's Life For Me (20 points) : Complete memory sequence 3.
No Apologies (20 points)           : Complete memory sequence 4.
Death Of A Salesman (20 points)    : Complete memory sequence 5.
Mixing Up The Medicines (20 points): Complete memory sequence 6.
The Hammer Falls (20 points)       : Complete memory sequence 7.
Adrift (20 points)                 : Complete memory sequence 8.
A New Hope (20 points)             : Complete memory sequence 9.
My Elusive Fortune (20 points)     : Complete memory sequence 10.
Been Down So Long... (20 points)   : Complete memory sequence 11.
Just Like Starting Over (20 points): Complete memory sequence 12. 
Saw That One Coming... (50 points) : Complete memory sequence 13.
By The Book (50 points)            : Complete 100% of all main mission constraints.
Silence, Fool! (5 points)          : Kill a guard ringing a bell.
Owned (10 points)                  : Complete every activity in a single location.
Vault Raider (30 points)           : Unlock the secret door in Tulum.
Killer Killer (10 points)          : Harpoon a killer whale.
Help A Brother Out (20 points)     : Complete a Templar Hunt sequence.
Sea Legs (30 points)               : Complete all naval contracts.
King Of The Castle (30 points)     : Capture all forts.
Employee Of The Month (30 points)  : Complete 25 Abstergo challenges.
Business And Pleasure (20 points)  : Earn 50,000 reales.
Mer-man (10 points)                : Swim a total of 1 nmi.
Redingote Up! (10 points)          : Craft the Hunter outfit.
Thug Life (30 points)              : Plunder 30 ships.
Devil Of The Caribbean (40 points) : Defeat all 4 legendary ships.
Destroyer (40 points)              : Fully upgrade the Jackdaw.
Seven Deadly Seas (10 points)      : Explore all underwater shipwrecks.
Barfly (30 points)                 : Unlock all taverns.
Cannon Fodder (5 points)           : Recruit 500 crew members.
FTFY (10 points)                   : Fully upgrade your hideout.
Cartographer (20 points)           : Visit every location of the game.
Ghost In The Machine (10 points)   : Hack 15 computers in Abstergo Entertainment.
Roped In (10 points)               : Perform 5 air assassinations from a swinging rope.
Sharing Is Caring (10 points)      : Share each type of discovery with friends once.
All Aboard! (30 points)            : Board a ship without losing any crew members.
Siren Song (20 points)             : Rescue pirate hostages by distracting enemies with "dancers."
Wild West Indies (20 points)       : Kill 4 enemies in a row using multi-pistols.
Excavator (10 points)              : Find a buried treasure.
Committed To The Cause (20 points) : Reach level 55 in Multiplayer.
Personal Bag Of Tricks (10 points) : Finish a game session with an ability set that 
                                     you customized in Multiplayer.
Master Of The Caribbean (20 points): Complete the Discovery Mode of Wolfpack in Multiplayer.
Lab Technician (10 points)         : Play and complete a game session of Game Lab in the 
                                     Multiplayer Public playlist.
All Rounder (20 points)            : Play on every game mode, and use every ability and ranged 
                                     weapon once in Multiplayer. 

Additionally, there are five secret achievements:
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Routine Hacking (20 points)           - Complete present day mission 2.
Getting Weird Around Here (20 points) - Complete present day mission 3.
Bunker Buddies (20 points)            - Complete present day mission 4.
It's All Good (20 points)             - Complete present day mission 5.
Hungover (10 points)                  - Wake up in a haystack. 

Giant squid attack Easter Egg:Swim inside the Antocha shipwreck at the 630, 660 coordinates. 
While looking out one of the windows, you should be able to see a giant squid take down a whale.