Was at our local marina today flying from the dock. Wanted to fly over some of the 150ft yachts for fun (large marina) in gps mode as to not drift into 90ft masts. Got half way down the marina bout 300m away and the thing went batshit crazy over the water.. went from 9 sats to zero and was pulling left and right full speed max tilt and losing altitude fast. Was able to recover as it got away from the spot and within seconds the sats counted back up to 9 and normal flight.. After safe landing, I spoke with marina staff about the interference and it turns out there is an area where all boats do not get gps signal, and of all places near the bathrooms at the center of the marina.. They have had the FCC come down to investigate but they could not find the source of the signal, its intermittent and not traceable. Major mystery!