From D&D Wiki
 Changes From the Original SRD
Added (from Abilities and Conditions):
- " extraordinary"
- "Water, particularly running water, ruins a trail for air-breathing creatures. Water-breathing creatures that have the scent ability, however, can use it in the water easily.
- "False, powerful odors can easily mask other scents. The presence of such an odor completely spoils the ability to properly detect or identify creatures, and the base Survival DC to track becomes 20 rather than 10."