Had a smallish hawksbill turtle in Thailand once swoop down from above just clipping the back of my head, probably current affected and it underestimated the effort to pass over me, it startled me but I didn't freekout.
Another one in the similians hanging off the dive platforming eating the rinds of watermelon the cook was throwing in. It was very photogenic, and clean shelled.
I have a spot here in Brisbane with very approachable turtles, its a cleaning station with always over a half a dozen large green and loggerhead turtles there hanging allowing the moon wrasse and rabbit fish to gnaw at the algae and barnicles on their back- I sometimes give em a scratch, if they seem happy to do so and I don't have a camera in hand, it gets the moon wrasse into a frenzy eating the fallout. They have done enormous damage to the staghorn coral in this site, its annual repairing making it all flatopped and solid like a slab of concrete, also some damage to the coral by a boat that sunk 25 years ago. There is no sea fans here probably because of turtles. This spot has had turtle there possibly for 10's of thousands of years. Bubble coral is very scarce and with the tiger sharks all but gone, it will become a problem with too many turtles here.
I have noticed smaller turtles following, but never the real big ones which seem to go about their own business or asleep with their heads tucked under a ledge(in which case I leave them well alone, don't even photo them).