It is not that the naturalists or shark or whale lovers don’t want you to Diving with Whale Sharks with the whale shark, it is the fact that you need not have to. They are water surface feeders and are slow docile just like mantas.
So all you need are a pair of flippers and a snorkel, but one of the reasons they SAY NO SCUBA DIVING is because then the diver will tend to go underneath where the whale sharks skin is most sensitive underneath.
Swimming with them is not a problem as they are docile and friendly and will not intentionally harm a human, maybe if you get to close to its tail and it smacks you with its swimming motion, but otherwise, no threat as it feeds on plankton.
But be aware stay at least five feet away from them as you touching them may cause them harm.