Water

You can tell which Micromon have a water element if the element icon next to their name looks like a drop of water.

These are vulnerable to wind attacks.

Water elemental attacks are effective against fire and mineral Micromon.

(Note that universal attacks like Bite or Scratch don't do elemental damage. These non-elemental attacks don't affect the Micromon's elemental weaknesses or strengths, regardless of the creature it's attacking or defending against.)