You've ventured into the depths of the jungle, fighting through thick undergrowth and dealing with all sorts of dangerous creatures. You have advantage on Resist Disease saves, and you don't suffer a perception penalty in rain.
Jungles are unforgiving landscapes that are among the most difficult to navigate. Starting at Level 12, you aren't slowed down by Hazardous Terrain or Slippery Terrain.
You've mastered the art of fighting in thick foliage. Starting at Level 22, as long as you're holding a one-handed bladed weapon, you can move at up to half your speed through foliage without making a skill check. You don't suffer a circumstance penalty on Perception for items concealed by foliage.