I have done a number of fish interactions with some of my characters and it always amuses me to see how I will create the fish and what their interaction will be. In this case it looks like they are diving deep. I know people go swimming with Whale sharks and other sea life( I haven’t done this yet)  but it seems a wonderful thing to do. As to being able to control the fish like a horse .. well I can barely control a bike and they have handle bars. Anyway , just another flight of fancy.