markwyner, These are Schooling Bannerfish, or False Moorish Idol. They live in external reef slopes of the Indo-Pacific region.
They’re captivating. 😍
More on the Bannerfish:
https://en.wikipedia.org/wiki/Schooling_bannerfish?wprov=sfti1Source:
https://www.instagram.com/reel/C1kJeTPNn1k/