While diving the Great Barrier Reef in 1983, had the great fortune to come across a manta ray with a 20' wing span, grab his shoulders, and be towed along the sea bed for a good long time. The most peaceful experience you can imagine.
While surfing in Morro Bay in 1980, I stepped on a sting ray and took a stinger in the heel. Incredibly painful - had to soak the foot in the hottest water tolerable for hours before it subsided.
I've since petted sting rays at aquariums many times.