Whilst playing through the main missions on this DLC you will unlock a quest called 'Mommy Issues'.
For this quest all you have to do is collect 3 parts of a weapon for a guy called Herbert (and his mother) to build. These parts are fairly straight forward to get.
One part requires a water launch which is done by diving into the water (
, whilst in the air) then pressing
which launches you out and onto the part which is being held by a crane above you.
Another piece just requires you to pick it up with the crane and the move the crane about 90 degrees to the left and dropping it onto some explosive barrels next to a bunch of Mooil Rig workers.
The last part is just lying there waiting for you to pick it up, easy peasy.
Just return the parts to Herbert and receive your rewards along with the achievement.