Since AlexDawson described so much compatibility of the Sea & Sea D800 housing with the D810 I went ahead and acquired that housing. Sadly, I cannot corroborate nearly as much functionality as he described.
Among the important functions that didn't work for me: rear command dial, info/menu/play/trash/mode buttons (these are in addition to the ones he said didn't work for him). However, I actually could hit the shutter release. Not sure why his gave him so much more functionality.
Many here have mentioned modifying their housings. Can anyone direct me to some guidance on this? I've never needed to do it, but would consider it for the time being. Some of the buttons appear to almost reach, even depressing buttons slightly but not enough for camera to notice. All I can think of is wrapping tape around inside button ends to bulk them up?
Big Island, Hawai'i
I just checked my functions again and aperture and shutter works perfect without any adjustments on my MDX-D800 with the Nikon D810
I will not modify anything on my housing unless I rely think I need the mode selector but usually I shoot in M.
Remember to place the camera in the housing with the switch on the housing to "ON" and turn the camera to "ON" before placing the camera inside the housing.