Utila is where people come to learn. It has been the cheap place to get certified for decades, and the island runs on divemaster trainees who arrived for a week and stayed for four months. The shops are strung along the single road behind the dock, most with their own jetty.
The whale sharks are the other reason. They pass close to the north shore in two seasons — roughly February to April and again October to December — and boats go out looking for the churning "boils" of tuna that give them away. Nobody can promise you a sighting; the shops that say otherwise are selling something they don't control.