https://phys.org/news/2018-06-reveals-secret-whale-shark-hotspots.html

Large groups of whale sharks congregate at only around 20 locations off the coasts of countries including Australia, Belize, the Maldives and Mexico. Why the sharks, which can reach more than 60 feet in length, choose these specific locations has long perplexed researchers and conservationists.

The new study, by researchers at the University of York in collaboration with the Maldives Whale Shark Research Programme (MWSRP), has found that the shark "aggregation sites" show many common characteristics—they are all in areas of warm, shallow water in close proximity to a sharp sea-floor drop off into deep water.