It is a Atlantic Blue Tang Acanthurus coeruleus. One thing it is not is a Chevron Tang Ctenochaetus hawaiiensis or a Yellow Eye Tang Ctenochaetus strigosus
As much trouble as we're all having IDing it, except for Boomer, I'm glad it isn't living in my tank...lol. It's bad enough we get all these hitchhikers we can't ID, I don't want a fish I can't ID....lol.