Toss loose items over the side
, if they run out of clothes call me
Seriously, get a garbage bag, pick up the flotsam and put it in the garbage bag; just tell 'em if they won't you will. Throw the bag on their berth (any of them at random).
Do the same thing with dishes, plates, etc.. food and all - right in with the clothes and other things left laying around.
No yelling, just a one time reading of the rules - loose items left laying in public spaces go into my 'you are screwed bag' I don't care what it is, who's it was or why you just forgot. You can have your item back at any time by getting it. If I find the same item twice in the same day it will fall overboard or into the real trash. Everyday I will clean the items in the bag for you by tossing it overboard and laundering it.
It's rough, it's tough, it's a angry dad reaction to kids being inconsiderate and
it is amazingly effective.
It takes once, just once and they get the message.
Works at home too - a plate full of food and glasses with soda etc. found under their pillow is a nice surprize; I figured they left it out thye were not done with it so I put it away for them