In answer to the question "Are these dangerous?": well, I suppose they could hit you with their tail by accident (I'm not convinced they even really know we are there...). They eat krill (wikipedia), so are basically filter feeders. Proportional to their size, their mouths are not that large and do not open that wide, and they don't really have teeth. According to Wikipedia, krill are particularly abundant in upwellings from the Humboldt current, which is part of the reason they are at Darwin Island. Most of the whale sharks there tend to be female and pregnant, but not that much is known about where they go and why. They have put a tracker on one, and saw it as far as Peru, where it disappeared (one hypothesis is that it went very deep).