Palworld

The oil rig is a new area in the Sakurajima update that can be found in the South East Ocean at about the coordinates 585,-430.

Upon approaching this area, there will be a LOT of rocket turrets and human enemies at level 55. If approaching by flying on a pal, your pal will be demolished by the rocket fire super quickly, so I recommend flying close, and then when the rocket turrets start firing, call back your pal and swim to the oil rig.

Also, something new with this update, the enemies will call forth their own pals to fight you.

At the base of each turret and tower on the oil rig is a control panel which you can use to destroy the turret/tower's functionality. I did this with all of them.
I then fought my way through, killing everything.
Eventually, in the rather built-up area of the rig, you will find some stairs going downstairs, and a room being guarded by two gatling-gun-wielding enemies.
Inside this room is a rocket turret (disable it!) and a large chest which takes ages to open.
The achievement only popped when I opened the chest.

To help, if you're standing in front of the chest, the coordinates on the map are 604,-420.