What is that grid structure at the very back. Hull protection?

Swim platform.

......so my weak attempt at humor was actually not so far off?

Well, i didn't believe you 74OA but yes i suppose it could be used for that and probably is.

Thanks RDC Ag. I thought it might be some sort of a protective measure if someone had to punch out just before landing but unless the hull is really thin there it would seem there are other far more vulnerable parts of the ship in an event like that.

Just in case anyone didn't know, the Navy does do open water swims. It is a bit of a pain, as it requires lots of approvals and even requires people to be on guard duty with rifles to shoot sharks, so it is kinda rare when it gets approved.

Article in Air & Space on this topic (swim call) - Everyone in the Ocean!

My Corps buddy who commanded General Dynamics Bath Iron Works says they are barge bumpers, as RDCAG described them. (Sorry, just saw your post)