Shipping/Cargo containers: Press V(hurtle) and the roll keys to glitch through the wall of the shipping container. Place turret as normal inside the container.

Underwater: Stand near water you want to place turret in, spawn turret in via warlords menu. walk/swim into water then place turret as normal.

Inside rubble: I have never personally watched someone do this one just seen the after effects of it. I think it works similar to the shipping container.