The horse in this song I have been told by many people represents weed wraped in brown paper. On another note the similarities are evident and almost undeniable the the song is about some type of drug: When he says "There was sand and hills and RAIN" This shows that there must be something dissoriented with what he is seeing (probably a hallucination. Later this is strangely countered by saying "It felt good to be out of the rain" This is odd and I never really got that. When he says "After nine days I let the horse run free cause the desert had turned to sea" this to my knowledge implies that he must have started to hallucinate too much and got scared so he threw away his weed for fear of seing more "rain" (weird or scary thing). "The ocean is a desert with it's life underground and a perfect disguise above" The Ocean representing the pinnacle of a buzz(or hi)and it is almost commemerating the drug, saying that it put a perfect disguise on life and makes it...awesome(couldn't think of a better word. "Under the cities lies a heart made of ground but the humans will give no love" Is reffering to the drugs secrecy and how people won't except that the altered reality during a hi. (I would like to point out that none of these ideas are specifically true this is just my sketch on the meaning of this bizzare song, It is one of those songs like "Smells like teen spirit" that will never be truly understood)
Take it from me, worrying about these type of things is not going to make you better at backing winners.