Last year, I saw an Asian movie on Tubi about three kids who go into a cave (actually, a large hole in the ground). When an earthquake-like event happens, one of the boys stays behind after the other two leave the cave. This boy stops ageing. The final shot at the end of the film shows the boy on a ship talking to a young girl. It's a wonderful story, but I can't remember the name of it.
Please note, this is not the 2017 film "Time Trap."