On our cruise the stateroom host was using the driftwood to indicate which room he was working on, or to remind him which room(s) he needed to stock with something else. I asked about this: our host said he (and some other hosts) use the wood to remind them to get, say, extra towels for that room before they finish their rounds. Maybe he ran out on the cart and needs to remember to get more before he finishes that area so he puts the wood on the fish as a reminder. Also helps him visually cue in to which room he was working on if he has to go do something else before he finishes. He said it can be hard to remember at times because things get hectic and "all the doors look alike" so the wood helps him pick up where he left off. Pretty crafty, I thought. Me, I'd just wander around aimlessly.