My rear passenger side(not the cargo area) carpet is wet.. What are the possible causes of water leak?
How much rain have you had?
Have you driven through any deep water?
Have you ever had any bodywork done to that side?
Mine leaked into the carpet on a creek crossing, but the sunroof drain starts down in that area also. Make sure it's clear by using a wire or plastic tube to clear out the drain from the bottom. You'll have to access them at the rocker openings.