I was at the helm when my ship (a Destroyer) went through the triangle. My compass went crazy and became useless.
Seas were a little choppy. Overcast sky. We had to call the captain to the bridge. I always hated going through there. One minute smooth seas, the next choppy.
I was a navigator in the CG and I sailed in those waters for 3 years and every single time we went into that area our gyro and magnetic compasses would also go completely nuts. There is definitely some magnetic abnormality in that area.