Three boats and sixteen seats across all of them, which is the entire pitch: you deal with the owner, and the person who sold you the trip is on the water with you rather than handing you to whoever has space.
Whale-shark regulations cap the boat at a small number of swimmers in the water at once anyway; what varies between operators is how many boats they are juggling and whether they resold your seat. This is the small end.
They publish no street address and no WhatsApp number — email or phone is how to reach them.