The melon-headed whale shark is occasional mainly because it typically life in intense waters, in which few folks go. And also the bonnethead shrimpfish is rare since it life entirely in salt h2o, where much less people go. All of these are excellent environments for rare fish to live in. https://www.diigo.com/item/note/9tt3x/whmt?k=e010b5903140773401617669db35102c