So I washed my car for the first time today and prior to this had no trouble with the rear door. So I go to put something in and the door won't budge. Figured it was locked but no. So I crawl in from the middle row and noticed a bit of water in the back. So where could it be coming from? The seals around the door? The handle??

 

Seals around the door or window are likely culprits.

For the door not opening pop the land rover emblem out of the handle cover spray liberally with wd40 or similar. push and pull the handle repeat till smooth.