E70 X5 Water in Rear Differential

[DieselGuy]

Hi guys, I'm new round here, but wanted to solicit some opinions on my situation.

I use the X5d to haul around a boat for short distances of less than 15mi each way to the lake. To launch, I have to back the car in the water until the exhaust is barely burbling on the water or where the water line is just about at the bmw symbol on the rear wheels.

The problem: I noticed a few drips of diff fluid on my garage floor and when I opened the plug nasty cream colored fluid came out. Lots of it. Theory goes, it filled with water and when heated, it was pushing the seals out causing the drip.

Question: How is water getting in? I haven't been able to find a vent or breather valve anywhere on the diff. Is the temp difference of a hot diff hitting cold water sucking water past the seals? How can I prevent this going forward other than changing the fluid constantly or trying not to back in to far on the boat launch?

Thoughts?