I drove around to the far back of the Subpen and promptly got destroyed. At that moment, I can't remember what happened, but I was pretty close to the inset of the Subpen and ended up being able to walk under and around the inset surrounding walkway. Took about a minute before I started to take very slow damage.
Same as the above, but this happened when trying to enter a Destroyer from the Allies Navel Yard. Again, was about to walk around all underneath the Naval Yard.