I've replaced BMW heads and head gaskets over the years and have seen real water in the oil. At worst, your dipstick pulls out and it looks like gray mayonnaise on it. Similar when you drain the oil.

If your drain looked fairly normal, most likely you had condensation from a year of moving the car a few car lengths with no warm up.

Do all the good things for the cooling system, even if you can't reach the drain plug on the block (socket extensions and U-joints may help).

Genuine BMW coolant or the BASF (from memory) OEM equivalent.