From Discworld MUD Wiki
A water room is a room that's underwater or on the surface of some water. Oceans, lakes, and rivers are all made up of water rooms.
- You need skill in adventuring.movement.swimming to move from room to room, or to avoid sinking. More burden makes it harder not to sink, and harder to swim up.
- You cannot journey through these terrains.
- Swimming around makes you wet and fills any open vessels you may have.
- Objects dropped will sink until they reach the bottom.
- Things cannot be dragged here.
- You can only bury things if they're on the bottom.
- If you "float", you will not resist the current (or sinking). You can "swim" to resist again.
On the surface
- Only the surface is technically "outdoors". The surface has weather, and a witch can fly to someone on the surface.
- Witches are naturally bouyant and need swimming skills to go under the surface.
- Finneblaugh's Thaumic Float lets you float above the water instead of sinking.
- If you stay underwater for too long without Breathe Underwater, you will start drowning. Some npcs can drown, while others are immune.
- You can portal when underwater, but you can only passage if you are using Breathe Underwater. Other rituals requiring the power of speech are also prevented if you do not have gills.
- It gets colder and darker as you go deeper.
- Under the surface, the map is more limited.