Answered by OP above, closing

You're a bit faster than the shark (3m/s vs 2m/s), but you're also much further away from the pontoon than it is (31m away vs. 13m away), which means it will get to the pontoon first and you will be eaten if you try to get past it.

It's a resolution with a different aspect ratio, so it's probably just a way to confuse people :)

Thank you, kind stranger, for saving me hours of despair!! I experienced the same issue and couldn't understand why nothing was being returned (I was sure it had something to do with the recursive function call, but I have very limited experience with them, so was struggling to work out where the problem was).

I'm curious as to why an X variable was included? As I understand it (and based on both my solution and all the others I've seen), only the Y is really necessary to answer the challenge. Is there another way of solving it that does use X, or is it just a red herring intended to trick people? :)

(I added the condition for dragons <= 0 because one of the random tests had dragons set to 0 and threw an error)