I can't confirm that to you. What I know is that there are excursions to view manta rays called "manta ray night dives"
I have not heard such thing and don't really think it has any basis. There are some who even use manta ray night dive during scuba diving
I once saw a Manta Ray at the beach and swam right next to it! Cool, did you get to see their triangular pectoral fins or forward-facing mouth? I actually did not. I heard Manta Rays were dangerous, is that true?
A manta ray night dive is a scuba diving excursion to view manta rays.