[Apologize for the long post] Sunday was a sad day for me. After dozens of successful long distance flights over the ocean, my last Phantom flight was a one way trip. My flight plan was a routine trip to the sea lions who occupy a buoy about 1.3 miles offshore, a flight I did two days prior. As before, I initiated the startup sequence from the bluffs 20 feet above the shoreline. The first indication that something was not right was the startup sequence of lights. The P2 immediately started flashing red/yellow instead of green/red. This was a compass error and I had never experienced it before. Very strange. Turned her off and on again. Same thing. I then performed a compass calibration, powered off, then on again. Now the normal green/red sequence appeared. All good I thought. As always I waited until the double rapid fire green lights before take off. As many of us know, fussing with you bird tends to draw a crowd. Three teenage boys and three adults were now watching. I took off normally and hovered for a few seconds. I remember thinking to myself that the P2 seemed to be having a hard time maintaining constant altitude and position. Seemed like it made a wide turn instead of a spin when I did a 180 yaw. But maybe it was my imagination. I continued to hover about 30 feet away so the kids could see themselves on the FPV screen. When I pointed toward the ocean and headed out, all seemed OK. Maintained 9 meters above my take off height and used the FPV to guide me to the oil rig 1.3 miles offshore. Hovered around for about 1 minute looking for the sea lion buoy but could not find it. Battery was at about 68% so I turned around and headed home. The problem happened when I was flying back. I was using the iOSD triangle to hit my home point, but something wasn't right. It seemed like it was coming in slow and drifting in a different direction (but maybe it was my imagination as drifting sometimes happens in ATTI mode). My FPV screen was starting to snow about 1500 meters out, which was unusual because it wasn't snowing as bad when I was further out. Normally I just flip to GPS mode, repoint the helical antenna and the antenna gets the signal back. But not this time. FPV never came back. I estimated I had about 50% battery left so I flicked the failsafe and prayed for a RTH. The people around me were quiet and probably sensed my internal panic. After 30 minutes of waiting I gave up and relinquished my Phantom2 to the ocean gods. Here's my take on what may have caused this 'flyaway' but I'm all ears for better explanations. There was definitely something screwy with the compass. The compass error at startup was not normal, and the motion of the P2 on the way home did not seem to make sense. Perhaps my recalibration did not "take" or was not effective. A bad compass would explain why it didn't return home when the F/S was activated. But I still can't understand the sudden loss of FPV video. Wish I had hooked up a DVR. One last factoid: After I flicked the F/S I noticed another guy flying his Phantom2 w/Zenmuse/GoPro about 100 feet from me. This was the same model as mine. Could it be that his signal caused my video to go out? I did not see any external antennas on his bird so I don't think he had FPV. (I did a channel scan but nothing came up on my monitor.) I toggled my RC sticks but it did not affect his Phantom. So perhaps there was no interference. I know flying FPV over water is inherently risky, but I had done it many times before and have gone much further out. I think this failure could have been prevented if my compass was working properly. Whether I mis-calibrated it or it was faulty is anyone's guess. In any case I contacted DJI and started a dialog. I want to get in the air again. As a good cu$tomer, I am hoping they will help defray the cost of a new P2. C'mon DJI! I'm not too upset, just kicking myself and wondering what I could have done to save her, if anything. I flew with this fear always in the back of my head. I just didn't think it would happen so soon! Thanks for listening.