If you leave a water-vulnerable item (books, scrolls, iron items) in a water tile, it will only be damaged after using a command to drop items while standing on that water tile. This leads to some illogical behavior:

1. If you use a drop command but decide not to drop anything, items on your square may be damaged despite no time actually passing.
2. Throwing or kicking an item into the water won't damage it, but dropping it can.
3. Water-vulnerable items can remain immersed in water indefinitely without being damaged.