Slightly OT, I was a life guard near Santa Cruz in 1971-2 during summers. On one of those endlessly boring summers(kinda vague, sorry) heard a load thrumming in the air..obviously a plane, but the engine sound was deep..soon spotted what looked like a Hellcat, dark blue almost black, at relatively low alt headed south, slowly, and I remember the cockpit canopy was slide back/open, the pilot didn't appear to have a hardshell helmet on, just flying'helmet'. I watched it tilll it dis-appeared, deep engine sound never missed a beat. Never saw another, in the air or on the ground.
JGroth