I live in florida and I have seen them fly like that.
It kinda freaked me out the first time, considering I was in the water and about 15 feet away!

there’s a lagoon just north of the space center in florida, at the canaveral national seashore, where mantas body surf the waves crashing through the mouth of the lagoon. i’ve seen some big enough to ride [16-22 feet wide from wingtip to wingtip.] i’m not fast enough to catch them but i hear it’s been done