I got tagged by a manta last month. We were diving Garden Eel Cove, the Kona manta dive site, during the day. We had mantas all over the place, a great dive. I was filming a manta make a pass just below me on the reef slope when she turned and came right at me, clipping me and the camera. No damage, just surprise.
I have the incident on video and ID'd the particular manta on the manta foundation website. She is a manta dive regular, has been for many years, with a 12' wingspan!
Mark made a great film of our dive that day, it does not include the bump, but shows how nice the mantas can be during the day...
[video]http://m.youtube.com/watch?v=34q3f1IksqE&[/video]