Thanks for the replies
As I said, I don't want to hurt the little darlings, just identify them, & perhaps get the into a bit of bother at home.
The only reason for the paint gun was a means of delivery of the pain balls, but it doesn't seem I can justify either of them on board
I rather like the idea of the super water pistol. I can justify that on board as 'adult' fun
I assume it can be filled with anything, maybe the Elsan (we only use it for liquids) before I put the blue in
Again many thanks for the sensible advice (& the fun ones!)