Assassin’s Creed IV: Seven Deadly Seas

At the beginning of sequence 06 (stroyline: Diving for Medicines) you get the diving bell, with the bell you can explore underwater shipwrecks.

divingbell

You dont need to fully explore a underwater shipwrecks, just lower the diving bell at all ten locations and the Achievement should pop, but should search trough every chest, becuase every underwater shipwrecks contains an upgrade plan (Destroyer Achievement). Here is a list of every location and the upgrade plan it contains

#1 – San Ignacio Wreck (379, 770) – Elite Hull
#2 – Antocha Wreck (630, 660)
#3 – The Black Trench (215, 449) – flower sails
#4 – San Juan (479, 487)
#5 – The Blue Hole (471, 170)
#6 – Kabah Ruins (769, 145)
#7 – Devil’s Eye Caverns (487, 357)
#8 – Anotto Bay (621, 277)
#9 – Ambergris Key (55, 178)
#10 – La Concepcion Wreck 181, 296)