With your answer, I have some new questions:
Q1: I get the swap after getting the double jump, that location is not in the map expansion but can I get to that location with a normal jump at the beginning of the game? Compared to the original Celestial, this game seems to lack dash.
Q2: Since I'm just getting normal fish over and over again in Fishing, and lacking a clear target, I checked the code (sorry). According to the calculations, if I need to get the double jump with a 50% probability, I need 266 successful fishing trips. Seems overly harsh on the success rate. (BTW, it actually took me an hour to get the double jump after fishing 136 fishes, so I don't know if I'm lucky or unlucky.)