I am now revising this post about the three Royal Terns I saw on the beach, one with a fish.  I had thought it was a parent with its young.  But I have been seeing some Laughing Gulls mating, and it occurred to me that maybe it's too early for young birds, but the right time for courtship.  An online search revealed that the male tern will present a fish to the female.  In that case, it is possible the other two terns are females, and the male is trying to get one of them interested in his fish.

He would fly away, circling around, but always coming back to the other two terns.  He did this several times, not trying to eat the fish, just showing it off.