The joy ride may have been fun, dangerous no, stupid yes. Everyplace I’ve ever been that has whalesharks prohibits this because it ticks off the whaleshark and they leave taking the tourist dollars with them.
In Holbox Mexoco we were told if one snorkeler touched the whaleshare the boat was going home and no refunds. The rulles were very clear, no touching and don’t get in their path. I did see a diver get on the back of a whaleshark and our Capitan called it in!
In the Galapagos, same rules but Scuba allowed. We did have on diver back roll off the panga onto the back of a hammerhead, now that could have been dangerous!