The obvious thing one can hold onto is a periscope, but it's also easy to get knocked off one by sudden water rushes, how that would work outside I don't know so maybe worth a try. You could even hook up the periscope to one of the weapons, maybe an external-only one. Maybe a ladder? I think they only work vertically and might look a bit odd, but perhaps you could build it into some sort of frame.

If making a mod then I would start with those two vanilla items.

Thankz for the suggestion ill give it a go and take notes as to what works