#1. After disabling the first defense battery, you now have to head to any of the two locations to disable the defense batteries. From your position, head to the northwest (open your map) and find another datapad inside the head of Lady Liberty.
#2. Go to the north and swim to the isolated building to the northwest. Here, you can help clear the Ceph forces to save your allied rebel mortar team as part of the secondary mission. Grab the datapad on the crate as well.
#3. After clearing Battery Bravo, continue southeast to trigger another secondary objective. Here you have to clear the mines around the rebel ICV. They're inside the cavern. Just open your nanovisor to hack the mines and clear the path. Head deeper inside to find a nanosuit upgrade, datapad and some ammo and arrows inside a wreckage.
#4. Further southeast is a downed helicopter, near the metal tentacle beside an island. You'll find this on the way to Battery Charlie. Head there to grab the datapad inside the wreckage.
#5. In the last area where you have to fight the Ceph Mastermind, you'll find the datapad in the corner, on top of some ammo crates.
Mastermind battle and last datapad acquisition