Water

Water is a liquid environment in Dungeon Keeper and Dungeon Keeper 2 that cannot be claimed or built on without the use of a Bridge (DK1) or Wooden or Stone Bridge (DK2).
The water itself is harmless, but in some levels can create openings in your base, leaving you open to attack, as well as being an inconvenience in any maps without bridges. Furthermore, in Dungeon Keeper 2, creatures are slowed in water, and take significantly more damage from nearby Lightning Traps.
== Dungeon Keeper==
Boulders crumble when they come into contact with water. Caution is still advised, however, as the boulder can still kill before it has hit the water.
Beware, diagonal and corner sections of earth will sometimes have a corner cubelet missing. This allows heroes and enemy creatures (as well as your own) to pass through diagonally, so try not to expose yourself in this way, and make sure to reinforce the walls there if possible and as quickly as you can.
==Dungeon Keeper 2==
"Water can be a most useful tactical asset, but it cannot be built upon. You can effectively claim areas of water (and allow your creatures free passage over them) by laying down a bridge."
Water works the same as it does in Dungeon Keeper, except it now has the property of slowing creatures. Vampires are unable to cross water at all, instead relying upon bridges or turning into bats to cross it.
Lightning Traps do more damage to creatures on water.
There is a hidden setting, 'Sine Wave Water', in the registry that, when enabled, makes the water ripple reminiscent of a sine wave: