Was actually thinking of a rain drop(s) running down the surface. If light can get in so can water, and the lens release button looks like the sort of place water could run into and divert into the camera.
Hi Expatinasia, have a look at this video, at around the 3.45 mark.https://www.youtube.com/watch?v=wUJc83wV6iA
I haven'y tried that with my own a7r, but I did have mine on a Jet Ski in Australia in December videoing my son on those Water Plume thingys, covered the a7r in a reasonable amount of salt water, washed it off later with a soaked towel of fresh water, still working, impressed me at least.
I've tried the light leak thing on mine, friend of mine also has the a7r we bought them same time same shop in Singapore, unable to get the light leak issue, but I can on my 5DMK III's, hasn't seemed to have caused much of an issue to date though.