Does being surrounded by water affect collisions between 2 bodies?

[DaveC426913]

What are the unknown unknowns in this context?

That ...
... is the $64,000 question. It is what these good people are trying to assess. But to do that, they need to know the application.For all we know, you're going to tell us '... for installation at the bottom of Lake Michigan' or '...for a military landing scaffold'.
and the experts here will say ... 'Ohhhh. No no no. You haven't factored in the whozitz of fresh water' or 'Wait, what grade of military steel are you cleared for?'

Or somesuch thing. Obvs these are facetious examples; the point is, they can't advise you as long as they can only see the scenario through a keyhole of your devising. The unknown unknowns are your unknowns.

That's kind of the PF way.

 

[berkeman]

One thing that is still an unknown for me is what-all this probe can bump into. I know @skywalker09 initially has been asking about impacting a flat plate, but what about other things in that environment like other ROV propellers, or cables, or batteries, or...